2006
Hallmann A
Morphogenesis in the family Volvocaceae:
Different tactics for turning an embryo right-side out
PROTIST 157 (4): 445-461 OCT 2006
Abstract: Green algae of the family Volvocaceae provide an
unrivalled opportunity to analyze an evolutionary pathway leading from
unicellularity to multicellularity with division of labor. One key step
required for achieving multicellularity in this group was the development of a
process for turning an embryo inside out: a morphogenetic process that is now
known as "inversion," and that is a diagnostic feature of the group.
Inversion is essential because at the end of its embryonic cleavage divisions,
each volvocacean embryo contains all of the cells that will be present in an
adult, but the flagellar ends of all cells are pointed toward the interior,
rather than toward the exterior where they will need to be to function in
locomotion. Inversion has been studied in greatest detail in Volvox
carteri, but although all other volvocacean species have to struggle with the
same awkward situation of being wrong-side out at the end of cleavage, they do
it in rather different ways. Here, the inversion processes of six different
volvocacean species (Gonium pectorale, Pandorina morum, Eudorina unicocca, Volvox
carteri, Volvox tertius, and Volvox globator) are compared, in
order to illustrate the variation in inversion patterns that exists within this
family. The simplest inversion process occurs in the plate-shaped alga Gonium
pectorale, and the most complicated in the spherical alga Volvox
globator Gonium pectorale goes only from a concave-bowl shape to a slightly
convex plate. In Volvox globator, the posterior hemisphere inverts
completely before the anterior pole opens and the anterior hemisphere slides
over the already-inverted posterior hemisphere; during both halves of this
inversion process, the regions of maximum cell-sheet curvature move
progressively, as radially symmetrical waves, along the posterior-anterior axis.
Fukada K, Inoue T, Shiraishi H
A posttranslationally regulated protease,
VheA, is involved in the liberation of juveniles from parental spheroids in Volvox
carteri
PLANT CELL 18 (10): 2554-2566 OCT 2006
Abstract: The lineage of volvocine algae includes unicellular
Chlamydomonas and multicellular Volvox in addition to their colonial
relatives intermediate in size and cell number. In an asexual life cycle,
daughter cells of Chlamydomonas hatch from parental cell walls soon after cell
division, while Volvox juveniles are released from parental spheroids
after the completion of various developmental events required for the survival
of multicellular juveniles. Thus, heterochronic change in the timing of
hatching is considered to have played an important role in the evolution of
multicellularity in volvocine algae. To study the hatching process in Volvox
carteri, we purified a 125- kD Volvox hatching enzyme ( VheA) from a
culture medium with enzymatic activity to degrade the parental spheroids. The
coding region of vheA contains a prodomain with a transmembrane segment, a
subtilisin- like Ser protease domain, and a functionally unknown domain,
although purified 125- kD VheA does not contain a prodomain. While 143- kD VheA
with a prodomain is synthesized long before the hatching stage, 125- kD VheA is
released into the culture medium during hatching due to cleavage processing at
the site between the prodomain and the subtilisin- like Ser protease domain,
indicating that posttranslational regulation is involved in the determination
of the timing of hatching.
Babinger K, Hallmann A, Schmitt R
Translational control of regA, a key gene
controlling cell differentiation in Volvox carteri
DEVELOPMENT 133 (20): 4045-4051
Abstract: The complete division of labour between the reproductive and
somatic cells of the green alga Volvox carteri is controlled by three
types of genes. One of these is the regA gene, which controls terminal
differentiation of the somatic cells. Here, we examined translational control
elements located in the 5' UTR of regA, particularly the eight upstream start
codons (AUGs) that have to be bypassed by the translation machinery before regA
can be translated. The results of our systematic mutational, structural and
functional analysis of the 5' UTR led us to conclude that a ribosome-shunting
mechanism-rather than leaky scanning, ribosomal reinitiation, or internal
ribosome entry site (IRES)-mediated initiation-controls the translation of regA
mRNA. This mechanism, which involves dissociation of the 40S initiation complex
from the message, followed by reattachment downstream, in order to bypass a
secondary structure block in the mRNA, was validated by deleting the predicted
'landing site' (which prevented regA expression) and inserting a stable 64 nucleotide
hairpin just upstream of this site (which did not prevent regA expression). We
believe that this is the first report suggesting that translation of an mRNA in
a green eukaryote is controlled by ribosome shunting.
Nozaki H, Ott FD, Coleman AW
Morphology, molecular phylogeny and
taxonomy of two new species of Pleodorina (Volvoceae, Chlorophyceae)
JOURNAL OF PHYCOLOGY 42 (5): 1072-1080 OCT 2006
Abstract: The volvocacean genus Pleodorina has been morphologically
characterized as having small somatic cells in spheroidal colonies and
anisogamous sexual reproduction with sperm packets. In this study we examined
two new species that can be assigned to the genus Pleodorina based on
morphology: P. starrii H. Nozaki et al. sp. nov. and P. thompsonii F. D. Ott et
al. sp. nov. P. starrii was collected from
Nedelcu AM, Michod RE
The evolutionary origin of an altruistic
gene
MOLECULAR BIOLOGY AND EVOLUTION 23 (8): 1460-1464 AUG 2006
Abstract: Although the conditions favoring altruism are being
increasingly understood, the evolutionary origins of the genetic basis for this
behavior remain elusive. Here, we show that reproductive altruism (i.e., a
sterile soma) in the multicellular green alga, Volvox carteri, evolved
via the co-option of a life-history gene whose expression in the unicellular
ancestor was conditioned on an environmental cue (as an adaptive strategy to
enhance survival at an immediate cost to reproduction) through shifting its
expression from a temporal (environmentally induced) into a spatial
(developmental) context. The gene belongs to a diverged and structurally
heterogeneous multigene family sharing a SAND-like domain (a DNA-binding module
involved in gene transcription regulation). To our knowledge, this is the first
example of a social gene specifically associated with reproductive altruism,
whose origin can be traced back to a solitary ancestor. These findings
complement recent proposals that the differentiation of sterile castes in
social insects involved the co-option of regulatory networks that control
sequential shifts between phases in the life cycle of solitary insects.
Duncan L, Nishii I, Howard A, et al.
Orthologs and paralogs of regA, a master
cell-type regulatory gene in Volvox carteri
CURRENT GENETICS 50 (1): 61-72 JUL 2006
Abstract: The multicellular green alga Volvox carteri forma
nagariensis has only two cell types: terminally differentiated somatic cells
and reproductive cells. The regA gene maintains the terminally differentiated
state of the somatic cells, apparently by repressing transcription of genes
required for chloroplast biogenesis and thereby preventing cell growth. Because
the RegA protein sequence bore no obvious motifs, we are attempting to identify
regions of functional importance by searching for strongly conserved domains in
RegA orthologs. Here we report the cloning and characterization of regA from
the most closely related known taxon, V. carteri f. kawasakiensis. Given the
closeness of the relationship between these two formas, their regA genes are
surprisingly different: they differ in the number of introns and by several
lengthy indels, and they encode proteins that are only 80% identical. We also
serendipitously discovered a paralogous gene immediately upstream of each regA
locus. The two regA genes, both upstream paralogs and several genes in
Chlamydomonas (the closest unicellular relative of Volvox) encode a
conserved region (the VARL domain) that contains what appears to be a
DNA-binding SAND domain. This discovery has opened up a new avenue for
exploring how regA and the terminally differentiated state that it controls
evolved.
Short MB,
Flows driven by flagella of multicellular
organisms enhance long-range molecular transport
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
103 (22): 8315-8319
Abstract: Evolution from unicellular organisms to larger multicellular
ones requires matching their needs to the rate of exchange of molecular
nutrients with the environment. This logistic problem poses a severe constraint
on development. For organisms whose body plan is a spherical shell, such as the
volvocine green algae, the current (molecules per second) of needed nutrients
grows quadratically with radius, whereas the rate at which diffusion alone
exchanges molecules grows linearly, leading to a bottleneck radius beyond which
the diffusive current cannot meet metabolic demands. By using Volvox
carteri, we examine the role that advection of fluid by the coordinated beating
of surface-mounted flagella plays in enhancing nutrient uptake and show that it
generates a boundary layer of concentration of the diffusing solute. That
concentration gradient produces an exchange rate that is quadratic in the
radius, as required, thus circumventing the bottleneck and facilitating
evolutionary transitions to multicellularity and germ-soma differentiation in
the volvocalean green algae.
Nedelcu AM
Evidence for p53-like-mediated stress
responses in green algae
FEBS LETTERS 580 (13): 3013-3017
Abstract: The tumor suppressor protein, p53, plays a major role
in cellular responses to stress and DNA damage in animals; despite its critical
function, p53 homologs have not been identified in any algal or plant lineage.
This study employs a functional and evolutionary approach to test for a p53
functional equivalent in green algae. Specifically, the study: (i) investigated
the effect of two synthetic compounds known to interfere with p53 activity;
(ii) searched for sequences with similarity to known p53-induced genes; and
(iii) analyzed the expression pattern of one such sequence. The findings
reported here suggest that a p53 functional equivalent is present and mediates
cellular responses to stress in green algae.
Hallmann A, Wodniok S
Swapped green algal promoters:
aphVIII-based gene constructs with Chlamydomonas flanking sequences work as dominant
selectable markers in Volvox and vice versa
PLANT CELL REPORTS 25 (6): 582-591 JUN 2006
Abstract: Production of transgenic organisms is a well-established,
versatile course of action in molecular biology. Genetic engineering often
requires heterologous, dominant antibiotic resistance genes that have been used
as selectable markers in many species. However, as heterologous 5' and 3'
flanking sequences often result in very low expression rates, endogenous
flanking sequences, especially promoters, are mostly required and are easily
obtained in model organisms, but it is much more complicated and time-consuming
to get appropriate sequences from less common organisms. In this paper, we show
that aminoglycoside 3'-phosphotransferase gene (aphVIII) based constructs with
3' and 5' untranslated flanking sequences (including promoters) from the
multicellular green alga Volvox work in the unicellular green alga
Chlamydomonas and flanking sequences from Chlamydomonas work in Volvox,
at least if a low expression rate is compensated by an enforced high gene
dosage. This strategy might be useful for all investigators that intend to
transform species in which genomic sequences are not available, but sequences
from related organisms exist.
Cheng Q, Hallmann A, Edwards L, et al.
Characterization of a
heat-shock-inducible hsp70 gene of the green alga Volvox carteri
GENE 371 (1): 112-120 APR 12 2006
Abstract: The green alga Volvox carteri possesses
several thousand cells, but just two cell types: large reproductive cells
called gonidia, and small, biflagellate somatic cells. Gortidia are derived
from large precursor cells that are created during embryogenesis by asymmetric
cell divisions. The J domain protein GlsA (Gonidia/ess A) is required for these
asymmetric divisions and is believed to function with an Hsp70 partner. As a
first step toward identifying this partner, we cloned and characterized V carleri
hsp70A, which is orthologous to HSP70A of the related alga Chlamydomonas
reinhardtii. Like HSP70A, V carleri hsp70A contains multiple heat shock
elements (HSEs) and is highly inducible by heat shock. Consistent with these
properties, Volvox transformants that harbor a glsA antisense transgene
that is driven by an hsp70A promoter fragment express Gls phenotypes that are
temperature-dependent. hsp70A appears to be the only gene in the genome that
encodes a cytoplasmic Hsp70, so we conclude that Hsp70A is clearly the best
candidate to be the chaperone that participates with GlsA in asymmetric cell
division.
Cheng Q, Balzer E, Miller SM, et al.
Effect of histone deacetylase inhibitors
on tubulin acetylation and development in Volvox carteri (Volvocales)
JOURNAL OF PHYCOLOGY 42 (2): 417-422 APR 2006
Abstract: Volvox carteri f. nagariensis (Iyengar) possesses
several thousand cells of just two types, gonida and somatic cells, that are
set apart by asymmetric cell division. Because the division apparatus contains
microtubules enriched in acetylated alpha-tubulin, we wished to know whether
acetylated tubulin plays any role in regulating division symmetry. Two
different human histone deacetylases (HDACs) have been shown to deacetylate
tubulin in vivo, thereby regulating cell motility. Here we set out to
determine: (1) whether HDAC inhibitors that increase tubulin acetylation in
animal cells have the same effect in V. carteri, (2) whether increasing
acetylated tubulin affects microtubule stability, and (3) whether increasing
acetylated tubulin affects division symmetry. Embryos exposed to two HDAC
inhibitors, trichostatin A (TSA) and tubacin, accrued dramatically higher
levels of acetylated tubulin (and more acetylated microtubules) and were
significantly more sensitive to colchicine than controls. However, while
TSA-treated embryos cleaved aberrantly to produce adults with abnormal
morphology, tubacin-treated embryos developed normally. We conclude that
increasing tubulin acetylation subtly alters microtubule stability, but does
not appear to affect cell division in V. carteri.
Michod RE, Viossat Y,
Life-history evolution and the origin of
multicellularity
JOURNAL OF THEORETICAL BIOLOGY 239 (2): 257-272
Abstract: The fitness of an evolutionary individual can be
understood in terms of its two basic components: survival and reproduction. As
embodied in current theory, trade-offs between these fitness components drive
the evolution of life-history traits in extant multicellular organisms. Here, we
argue that the evolution of germ-soma specialization and the emergence of
individuality at a new higher level during the transition from unicellular to
multicellular organisms are also consequences of trade-offs between the two
components of fitness-survival and reproduction. The models presented here
explore fitness trade-offs at both the cell and group levels during the
unicellular-multicellular transition. When the two components of fitness
negatively covary at the lower level there is an enhanced fitness at the group
level equal to the covariance of components at the lower level. We show that
the group fitness trade-offs are initially determined by the cell level
trade-offs. However, as the transition proceeds to multicellularity, the group
level trade-offs depart from the cell level ones, because certain fitness
advantages of cell specialization may be realized only by the group. The
curvature of the trade-off between fitness components is a basic issue in
life-history theory and we predict that this Curvature is concave in
single-celled organisms but becomes increasingly convex as group size increases
in multicellular organisms. We argue that the increasingly convex curvature of
the trade-off function is driven by the initial cost of reproduction to Survival
which increases as group size increases. To illustrate the principles and
conclusions of the model, we consider aspects of the biology of the volvocine
green algae, which contain both unicellular and multicellular members.
A hydrodynamics approach to the evolution
of multicellularity: Flagellar motility and germ-soma differentiation in
volvocalean green algae
AMERICAN NATURALIST 167 (4): 537-554 APR 2006
Abstract: During the unicellular-multicellular transition, there are
opportunities and costs associated with larger size. We argue that germ-soma
separation evolved to counteract the increasing costs and requirements of
larger multicellular colonies. Volvocalean green algae are uniquely suited for
studying this transition because they range from unicells to multicellular
individuals with germ-soma separation. Because Volvocales need flagellar
beating for movement and to avoid sinking, their motility is modeled and
analyzed experimentally using standard hydrodynamics. We provide comparative
hydrodynamic data of an algal lineage composed of organisms of different sizes
and degrees of complexity. In agreement with and extending the insights of
Koufopanou, we show that the increase in cell specialization as colony size
increases can be explained in terms of increased motility requirements. First,
as colony size increases, soma must evolve, the somatic-to-reproductive cell
ratio increasing to keep colonies buoyant and motile. Second, increased
germ-soma specialization in larger colonies increases motility capabilities
because internalization of non-flagellated germ cells decreases colony drag.
Third, our analysis yields a limiting maximum size of the volvocalean spheroid
that agrees with the sizes of the largest species known. Finally, the different
colony designs in Volvocales reflect the trade-offs between reproduction,
colony size, and motility.
Multicellularity and the functional
interdependence of motility and molecular transport
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
103 (5): 1353-1358
Abstract: Benefits, costs, and requirements accompany the transition
from motile totipotent unicellular organisms to multicellular organisms having
cells specialized into reproductive (germ) and vegetative (sterile soma)
functions such as motility. In flagellated colonial organisms such as the
volvocalean green algae, organized beating by the somatic cells' flagella
yields propulsion important in phototaxis and chemotaxis. It has not been
generally appreciated that for the larger colonies flagellar stirring of
boundary layers and remote transport are fundamental for maintaining a
sufficient rate of metabolite turnover, one not attainable by diffusive
transport alone. Here, we describe experiments that quantify the role of
advective dynamics in enhancing productivity in germ soma-differentiated
colonies. First, experiments with suspended deflagellated colonies of Volvox
carteri show that forced advection improves productivity. Second, particle
imaging velocimetry of fluid motion around colonies immobilized by micropipette
aspiration reveals flow fields with very large characteristic velocities U
extending to length scales exceeding the colony radius R. For a typical
metabolite diffusion constant D, the associated Peclet number Pe = 2UR/D
>> 1, indicative of the dominance of advection over diffusion, with
striking augmentation at the cell division stage. Near the colony surface,
flows generated by flagella can be chaotic, exhibiting mixing due to stretching
and folding. These results imply that hydrodynamic transport external to
colonies provides a crucial boundary condition, a source for supplying internal
diffusional dynamics.
Hallmann A
The pherophorins: common, versatile
building blocks in the evolution of extracellular matrix architecture in
Volvocales
PLANT JOURNAL 45 (2): 292-307 JAN 2006
Abstract: Green algae of the order Volvocales provide an
unrivalled opportunity for exploring the transition from unicellularity to
multicellularity. They range from unicells, like Chlamydomonas, through
homocytic colonial forms with increasing cooperation of individual cells, like
Gonium or Pandorina, to heterocytic multicellular forms with different cell
types and a complete division of labour, like Volvox. A fundamental
requirement for the evolution of multicellularity is the development of a
complex, multifunctional extracellular matrix (ECM). The ECM has many
functions, which can change under developmental control or as a result of
environmental factors. Here molecular data from 15 novel proteins are
presented. These proteins have been identified in Chlamydomonas reinhardtii,
Gonium pectorale, Pandorina morum and Volvox carteri, and all belong to
a single protein family, the pherophorins. Pherophorin-V1 is shown to be a
glycoprotein localized to the 'cellular zone' of the V. carteri ECM.
Pherophorin-V1 and -V2 mRNAs are strongly induced not only by the sex inducer,
which triggers sexual development at extremely low concentrations, but also by
mechanical wounding. Like the extensins of higher plants, which are also
developmentally controlled or sometimes inducible by wounding, the pherophorins
contain a (hydroxy-) proline-rich (HR) rod-like domain and are abundant within
the extracellular compartment. In contrast to most extensins, pherophorins have
additional globular A and B domains on both ends of the HR domains. Therefore
pherophorins most closely resemble a particular class of higher plant extensin,
the solanaceous lectins (e. g. potato lectin), suggesting multivalent
carbohydrate-binding functions are present within the A and B domains and are
responsible for cross-linking. Our results suggest that pherophorins are used
as the building blocks for the extracellular scaffold throughout the
Volvocales, with the characteristic mesh sizes in different ECM structures
being a result of the highly diverse extensions of the HR domains. Pherophorins
have therefore been a versatile element during the evolution of ECM
architecture in these green algae.
2005
Yoshida H, Yokomori T, Suyama A. A simple classification of the volvocine algae by formal languages.
BULLETIN OF MATHEMATICAL BIOLOGY 67 (6): 1339-1354 NOV 2005
Abstract: There
are several explanations of why certain primitive multicellular organisms
aggregate in particular forms and why their constituent cells cooperate with
one another to a particular degree. Utilizing the framework of formal language
theory, we have derived one possible simple classification of the volvocine
algae-one of the primitive multicells-for some forms of aggregation and some
degrees of cooperation among cells. The volvocine algae range from the unicellular
Chlamydonionas to the multicellular Volvox globator, which has thousands of
cells. The classification we use in this paper is based on the complexity of
Parikh sets of families on Chomsky hierarchy in formal language theory. We show
that an alga with almost no space closed to the environment, e.g., Gonium
pectorale, can be characterized by PsFIN, one with a closed space and no
cooperation, e.g., Eudorina elegans, by PsCF, and one with a closed space and
cooperation, e.g., Volvox globator, by Ps lambda SC. This classification should
provide new insights into the necessity for specific forms and degrees of
cooperation in the volvocine algae. (c) 2005 Society for Mathematical Biology.
Cheng Q, Pappas V, Hallmann A, et
al. Hsp70A and GlsA interact as
partner chaperones to regulate asymmetric division in Volvox. DEVELOPMENTAL BIOLOGY 286 (2):
537-548
Abstract: GlsA, a J-protein chaperone, is required for the asymmetric divisions that set aside germ and somatic cell precursors during embryogenesis in Volox carteri, and previous evidence indicated that this function requires an intact Hsp70-binding site. To determine if Hsp70A, the only known cytoplasmic Hsp70 in V. carteri, is the chaperone partner of GlsA, we investigated the localization of the two proteins during critical stages of embryogenesis and tested their capacity to interact. We found that a substantial fraction of Hsp70A co-localizes with GlsA, both in interphase and mitotic blastomeres. In addition, Hsp70A coimmunoprecipitated with GlsA, and co-expression of GlsA and Hsp70A variants partially rescued the Gls phenotype of a glsA mutant, whereas neither variant by itself rescued the mutant phenotype. Immunofluorescence analysis demonstrated that GlsA is about equally abundant in all blastomeres at all cleavage stages examined but that Hsp70A is more abundant in anterior (asymmetrically dividing) blastomeres than in posterior (symmetrically dividing) blastomeres during the period of asymmetric division. We conclude that Hsp70A and GlsA function as chaperone partners that regulate asymmetric division and that the relative abundance of Hsp70A in asymmetrically dividing embryos may determine which blastomeres divide asymmetrically and which do not.
Aono N, Inoue T, Shiraishi H. Genes specifically expressed in sexually differentiated female spheroids of Volvox carteri.
JOURNAL OF BIOCHEMISTRY 138 (4): 375-382 OCT 2005
Abstract: Volvox
carteri is a multicellular green alga with only two cell types, somatic cells
and reproductive cells. Phylogenetic analysis suggests that this organism has
evolved from a Chlamydomonas-like unicellular ancestor along with
multicellularity, cellular differentiation, and a change in the mode of sexual
reproduction from isogamy to oogamy. To examine the mechanism of sexual
differentiation and the evolution of oogamy, we isolated 6 different cDNA
sequences specifically expressed in sexually differentiated female spheroids.
The genes for the cDNAs were designated SEF1 to SEF6. The time course of
accumulation of each mRNA was shown to be distinct. The expression of some of
these genes was not significantly affected when the sexual inducer was removed
after the induction of sexual development. Sequence analysis indicates that
SEF5 and SEF6 encode pherophorin-related proteins. Of these, SEF5 has the
unique structural feature of a polyproline stretch in the C-terminal domain in
addition to the one found in the central region.
Wadhwa V, Kumar S, Rai S, et al. A
'pseudo outbreak' of the contamination of blood cultures with Volvox
globator.
ANNALS OF TROPICAL MEDICINE AND
PARASITOLOGY 99 (7): 719-720 OCT 2005
2004
Kirk MM,
Kirk DL
Exploring germ-soma differentiation in Volvox
JOURNAL OF BIOSCIENCES 29 (2): 143-152 JUN 2004
Just A,
Gruber I, Wober M, et al.
Novel method for the cryopreservation of testicular sperm and ejaculated
spermatozoa from patients with severe oligospermia: a pilot study
FERTILITY AND STERILITY 82 (2): 445-447 AUG 2004
Abstract:
Objective:
To investigate Volvox globator as an easy-to-handle vehicle and as a
safe alternative for cryopreservation of functional motile sperm cells.
Design: Prospective, controlled,
clinical pilot study.
Setting: Two in vitro
fertilization (IVF) outpatient clinics for reproductive medicine.
Patient(s): Fifteen patients with
severe male infertility (density <100 motile sperm per milliliter) who were
recruited from two IVF programs. The sperm cells were not intended for clinical
use after thawing.
Intervention(s): In each case, a
predetermined number (n = 8) of motile and morphologically intact sperm cells
were injected into each Volvox sphere and then cryopreserved. The
quality of the sperm cells and the handling of the Volvox spheres were
verified.
Main Outcome Measure(s): Postthaw
recovery rate in cases of severe male infertility and the amount of motile
sperm after thawing.
Result(s): The postthaw recovery
rate was 100%. At least 60% of the sperm cells were motile after thawing.
Conclusion(s): The use of the
spherical algae Volvox globator offers a promising, inexpensive, and
easy approach to the cryopreservation of functional motile sperm cells. Volvox
globator is an alternative in countries that prohibit the destructive use of
oocytes, even after fertilization has failed.
Jakobiak T,
Mages W, Scharf B, et al.
The bacterial paromomycin resistance gene, aphH, as a dominant selectable
marker in Volvox carteri
PROTIST 155 (4): 381-393 DEC 2004
Abstract:
The aminoglycoside antibiotic paromomycin that is highly toxic to the green alga Volvox carteri is efficiently inactivated by aminoglycoside 3'-phosphotransferase from Streptomyces rimosus. Therefore, we made constructs in which the bacterial aphH gene encoding this enzyme was combined with Volvox cis-regulatory elements in an attempt to develop a new dominant selectable marker - paromomycin resistance (Pm-R) - for use in Volvox nuclear transformation. The construct that provided the most efficient transformation was one in which aphH was placed between a chimeric promoter that was generated by fusing the Volvox hsp70 and rbcS3 promoters and the 3' UTR of the Volvox rbcS3 gene. When this plasmid was used in combination with a high-impact biolistic device, the frequency of stable Pm-R transformants ranged about 15 per 106 target cells. Due to rapid and sharp selection, Pm-R transformants were readily isolated after six days, which is half the time required for previously used markers. Co-transformation of an unselected marker ranged about 30%. The chimeric aphH gene was stably integrated into the Volvox genome, frequently as tandem multiple copies, and was expressed at a level that made selection of Pm-R transformants simple and unambiguous. This makes the engineered bacterial aphH gene an efficient dominant selection marker for the transformation and co-transformation of a broad range of V carteri strains without the recurring need for using auxotrophic recipient strains.
Pappas V,
Blakely S, Wetzel M, et al.
Functional analysis of the Volvox asymmetric division protein GlsA
MOLECULAR BIOLOGY OF THE CELL 15: 218A-218A 1207 Suppl. S NOV 2004
Cheng Q,
Miller SM
Cytoplasmic Hsp70 distribution correlates with asymmetric division in the
green alga Volvox carteri
MOLECULAR BIOLOGY OF THE CELL 15: 218A-218A 1206 Suppl. S NOV 2004
Kirk DL
Volvox
CURRENT BIOLOGY, 14, R599-R600;
for pdf click here
Nedelcu AM, Marcu O, and Michod
RE.
Sex as a response
to oxidative stress: A two-fold increase in cellular reactive oxygen species
activates sex genes.
P ROY SOC LOND B BIO, 271, 1591-1596; for pdf click here
Abstract:
Organisms are constantly subjected to factors that can alter the cellular redox balance and result in the formation of a series of highly reactive molecules known as reactive oxygen species (ROS). As ROS can be damaging to biological structures, cells evolved a series of mechanisms (e.g., cell-cycle arrest, programmed cell death) to respond to high levels of ROS (i.e., oxidative stress). Recently, we presented evidence that in a facultatively sexual lineage – the multicellular green alga Volvox carteri – sex is an additional response to increased levels of stress, and likely ROS and DNA damage. Here, we show that in V. carteri (i) sex is triggered by a ca. two-fold increase in the level of cellular ROS (induced either by the natural sex-inducing stress, namely heat, or by blocking the mitochondrial electron transport chain with antimycin A), and (ii) ROS are responsible for the activation of sex genes. As most types of stress result in the overproduction of ROS, we believe that our findings will prove to extend to other facultatively sexual lineages, which could be indicative of the ancestral role of sex as an adaptive response to stress and ROS-induced DNA damage.
Nedelcu AM and Michod RE.
Evolvability,
modularity, and individuality during the transition to multicellularity
in volvocalean green algae.
In
Schlosser G and Wagner G (eds) “Modularity in development and evolution”.
Pp. 466-489.
2003
Peculiarities of the geographical
distribution of coenobial volvocine algae (Volvocaceae, Chlorophyta).
Botanical Journal (
Abstract:
Data on the geographical distribution of 36 species from 7 genera of the family Volvocaceae sensu Nozaki (Pandorina, Volvulina, Yamagishiella, Eudorina, Platydorina, Pleodorina and Volvox) have been summarized. Both cosmopolitan species and species with local distribution have been detected. An attempt was made to trace a correlation of latitudinal distribution of the coenobial volvocine algae with obligatory differentiated somatic cells (22 species of the genera Volvox and Pleodorina) with peculiarities of proceeding of the cell divisions during asexual developmental cycle. In high latitudes of the Northern Hemisphere (northward of 50-57° north) only 3 species of Volvox occur, in which the formation of new coenobia (a series of consecutive gonidial divisions) starts with the light period (in the morning), the rate of division is slow and the gonidial divisions are temporarily blocked in darkness.
Schmitt
R
Differention
of germinal and somatic cells in Volvox
carteri
CURRENT OPINION IN MICROBIOLOGY
6 (6): 608-613 DEC 2003
Abstract:
Volvox carteri is a spherical alga with a complete division of labor between
around 2000 biflagellate somatic cells and 16 asexual reproductive cells
(gonidia). It provides an attractive system for studying how a molecular
genetic program for cell-autonomous differentiation is encoded within the
genome. Three types of genes have been identified as key players in germ-soma
differentiation: a set of gls genes that act in the embryo to shift
cell-division planes, resulting in asymmetric divisions that set apart the
large-small sister-cell pairs; a set of lag genes that act in the large
gonidial initials to prevent somatic differentiation; and the regA gene, which
acts in the small somatic initials to prevent reproductive development.
Somatic-cell-specific expression of regA is controlled by intronic enhancer and
silencer elements.
Nozaki H
Origin and
evolution of the genera Pleodorina and Volvox
(Volvocales)
BIOLOGIA 58 (4): 425-431 JUL 2003
Abstract:
The previous molecular phylogenetic study using 6021 base pairs from five
chloroplast genes suggested that two species of Pleodorina (P. californica, P.
japonica) might have evolved from a Volvox-like alga by the decrease in colony
cell number and size. However, number of species of the genus Volvox was very
limited especially in the section Merrillosphaera. In
the present study, 6021 base pairs of the concatenated five chloroplast genes
from 10 strains representing seven taxa of the genus Volvox were added to the
previous data matrix. The sequence data resolved two anisogamous/oogamous
clades within a large monophyletic group comprising five advanced genera of the
Volvocaceae (Yamagishiella, Platydorina, Eudorina, Pleodorina and Volvox), one
containing Volvox sect. Volvox and the anisogamous genus Platydorina (32-celled
flattened colony), and the other (Eudorina group) composed of three other
sections of Volvox, Pleodorina and Eudorina. The isogamous genus Yamagishiella
(32-celled colony) was positioned basally to the Eudorina group. Therefore,
evolution of anisogamy with sperm packets from isogamy might have occurred
twice within the Volvocaceae. Based on the present molecular phylogenetic
analysis, species of Volvox and Pleodorina within the Eudorina group
represented three and two, respectively, separate lineages. One the three
Volvox lineages [composed of V (sect. Merrillosphaera) carteri, V (sect.
Merrillosphaera) obversus, V. (sect. Merrillosphaera) tertius, V. (sect.
Merrillosphaera) africanus and V (sect. Copelandosphaera) dissipatrix] was
sister to the monophyletic group consisting of one of the two Pleodorina
lineages (P. californica and P. japonica) and V (sect. Janetosphaera) aureus.
In addition, species of Eudorina were basal to the two lineages of Pleodorina
and three Volvox lineages within the Eudorina group, representing the ancestral
situation of Pleodorina/Volvox (excluding sect. Volvox). Thus, reverse
evolution from a Volvox-like alga to Pleodorina suggested previously appears
unlikely.
Cheng
Q, Fowler R, Tam LW, et al.
The role of GlsA
in the evolution of asymmetric cell division in the green alga Volvox caiteri
DEV GENES EVOL 213 (7): 328-335 JUL 2003
Abstract:
Volvox carteri, a green alga in the order Volvocales, contains two completely
differentiated cell types, small motile somatic cells and large reproductive cells
called gonidia, that are set apart from each other during embryogenesis by a
series of visibly asymmetric cell divisions. Mutational analysis has revealed a
class of genes (gonidialess, gls) that are required specifically for asymmetric
divisions in V. carteri, but that are dispensable for symmetric divisions.
Previously we cloned one of these genes, glsA, and showed that it encodes a
chaperone-like protein (G1sA) that has close orthologs in a diverse set of
eukaryotes, ranging from fungi to vertebrates and higher plants. In the present
study we set out to explore the role of glsA in the evolution of asymmetric
division in the volvocine algae by cloning and characterizing a glsA ortholog
from one of the simplest members of the group, Chlamydomonas reinhardtii, which
does not undergo asymmetric divisions. This ortholog (which we have named gar1,
for glsA related) is predicted to encode a protein that is 70% identical to
G1sA overall, and that is most closely related to G1sA in the same domains that
are most highly conserved between G1sA and its other known orthologs. We report
that a gar1 transgene fully complements the glsA mutation in V. carteri, a
result that suggests that asymmetric division probably arose through the
modification of a gene whose product interacts with G1sA, but not through a
modification of glsA itself.
Grewing
A, Krings M, Galtier J, et al.
The oldest fossil
endophytic alga and its unusual habitat
SYMBIOSIS 34 (3): 215-230 2003
Abstract:
Lycophyte megaspores from the Lower Carboniferous of France sometimes contain a
colonial (volvocacean) alga as an endophyte. This peculiar plant-plant
association was briefly described more than 100 years ago and the name
Lageniastrum macrosporae introduced for the alga, but the biological
significance of the discovery was never fully appreciated. Here we present a
reappraisal of the original material, which to date provides the oldest
unequivocal fossil evidence for endophytic algae and the only example of an
alga residing in the interior of spores of vascular cryptogams.
Nedelcu
AM, Michod RE
Sex as a response
to oxidative stress: the effect of antioxidants on sexual induction in a
facultatively sexual lineage
P ROY SOC LOND B BIO 270: S136-S139 Suppl. 2
Abstract:
The evolution of sex is one of the long-standing unsolved problems in biology.
Although in many lineages sex is an obligatory part of the life cycle and is
associated with reproduction, in prokaryotes and many lower eukaryotes, sex is
facultative, occurs in response to stress and often involves the formation of a
stress-resistant dormant form. The proximate and ultimate causes of the
connection between stress and sex in facultatively sexual lineages are unclear.
Because most forms of stress result in the overproduction of cellular reactive
oxygen species (ROS), we address the hypothesis that this connection involves
ROS and possibly reflects the ancestral role of sex as an adaptive response to
the damaging effects of stress-induced ROS (i.e. oxidative stress) . Here, we report
that two antioxidants inhibit sexual induction in a facultatively sexual
species-the multicellular green alga, Volvox carteri. Furthermore, the
nature of the sex response and the effect of an iron chelator on sexual
induction are consistent with sex being a response to the DNA-damaging effects
of ROS. In addition, we present preliminary data to suggest that sex,
cell-cycle arrest and apoptosis are alternative responses to increased levels
of oxidative stress.
Rudel
D, Sommer RJ
The evolution of
developmental mechanisms
DEV BIOL 264 (1): 15-37 DEC 1 2003
Abstract:
Over the past two to three decades, developmental biology has demonstrated that
all multicellular organisms in the animal kingdom share many of the same
molecular building blocks and many of the same regulatory genetic pathways. Yet
we still do not understand how the various organisms use these molecules and
pathways to assume all the forms we know today. Evolutionary developmental
biology tackles this problem by comparing the development of one organism to
another and comparing the genes involved and gene functions to understand what
makes one organism different from another. In this review, we revisit a set of
seven concepts defined by Lewis Wolpert (fate maps, asymmetric division.
induction, competence, positional information, determination, and lateral
inhibition) that describe the characters of many developmental systems and
supplement them with three additional concepts (developmental genomics, genetic
redundancy, and genetic networks). We will discuss examples of comparative
developmental studies where these concepts have guided observations on the
advent of a developmental novelty. Finally, we identify a set of evolutionary
frameworks, such as developmental constraints, cooption, duplication, parallel
and convergent evolution, and homoplasy, to adequately describe the
evolutionary properties of developmental systems. (C) 2003 Elsevier Inc. All
rights reserved.
Kato-Minoura
T, Okumura M, Hirono M, et al.
A novel family of
unconventional actins in volvocalean algae
J MOL EVOL 57 (5): 555-561 NOV 2003
Abstract:
The unicellular green alga Chlamydomonas reinhardtii has two actin genes, one
encoding a conventional actin (90% amino acid identity with mammalian actin),
the other a highly divergent actin (64% identity) named novel actin-like
protein (NAP). To see whether the presence of conventional and unconventional
actins in a single organism is unique to C. reinhardtii, we searched for
genomic sequences related to the NAP sequence in several other species of
volvocalean algae. Here we show that Chlamydomonas moewusii and Volvox carteri
also have, in addition to a conventional actin, an unconventional actin similar
to the C. reinhardtii NAP. Analyses of the deduced protein sequences indicated
that the NAP homologues form a distinct group derived from conventional actin.
Golstein
P, Aubry L, Levraud JP
Cell-death
alternative model organisms: Why and which?
NAT REV MOL CELL BIO 4 (10): 798-807 OCT 2003
Abstract:
Classical model organisms have helped greatly in our understanding of cell
death but, at the same time, night have constrained it. The use of other,
nor-classical model organisms from all biological kingdoms could reveal
undetected molecular pathways and better-defined morphological types of cell
death. Here we discuss what is known and what might be learned from these
alternative model systems.
Ohta H,
Suzuki T, Ueno M, et al.
Extrinsic proteins
of photosystem II - An intermediate member of the PsbQ protein family in red
algal PSII
EUR J BIOCHEM 270 (20): 4156-4163 OCT 2003
Abstract:
The oxygen-evolving photosystem II (PS II) complex of red algae contains four
extrinsic proteins of 12 kDa, 20 kDa, 33 kDa and cyt c-550, among which the 20
kDa protein is unique in that it is not found in other organisms. We cloned the
gene for the 20-kDa protein from a red alga Cyanidium caldarium. The gene
consists of a leader sequence which can be divided into two parts: one for
transfer across the plastid envelope and the other for transfer into thylakoid
lumen, indicating that the gene is encoded by the nuclear genome. The sequence
of the mature 20-kDa protein has low but significant homology with the
extrinsic 17-kDa (PsbQ) protein of PS II from green algae Volvox Carteri
and Chlamydomonas reinhardtii, as well as the PsbQ protein of higher plants and
PsbQ-like protein from cyanobacteria. Cross-reconstitution experiments with
combinations of the extrinsic proteins and PS Its from the red alga Cy.
caldarium and green alga
Cole
DG, Reedy MV
Algal
morphogenesis: How Volvox turns
itself inside-out
CURR BIOL 13 (19): R770-R772
Abstract:
During its development, the multicellular green alga Volvox undergoes
inversion, in which spherical embryos turn their multicellular sheet completely
inside out. A mutant analysis has revealed that a novel kinesin motor protein
is essential for completing this process.
Voigt
J, Frank R
14-3-3 proteins
are constituents of the insoluble glycoprotein framework of the Chlamydomonas
cell wall
PLANT CELL 15 (6): 1399-1413 JUN 2003
Abstract:
The cell wall of the unicellular green alga Chlamydomonas reinhardtii consists
predominantly of Hyp-rich glycoproteins, which also occur in the extracellular
matrix of multicellular green algae and higher plants. In addition to the
Hyp-rich polypeptides, the insoluble glycoprotein framework of the
Chlamydomonas cell wall contains minor amounts of
Michod
RE, Nedelcu AM
On the
reorganization of fitness during evolutionary transitions in individuality
INTEGR COMP BIOL 43 (1): 64-73 FEB 2003
(for pdf click here)
Abstract:
The basic problem in an evolutionary transition is to understand how a group of
individuals becomes a new kind of individual, possessing the property of
heritable variation in fitness at the new level of organization. During an
evolutionary transition, for example, from single cells to multicellular
organisms, the new higher-level evolutionary unit (multicellular organism)
gains its emergent properties by virtue of the interactions among lower-level
units (cells). We see the formation of cooperative interactions among
lower-level units as a necessary step in evolutionary transitions; only
cooperation transfers fitness from lower levels (costs to group members) to
higher levels (benefits to the group). As cooperation creates new levels of
fitness, it creates the opportunity for conflict between levels as deleterious
mutants arise and spread within the group. Fundamental to the emergence of a
new higher-level unit is the mediation of conflict among lower-level units in
favor of the higher-level unit. The acquisition of heritable variation in
fitness at the new level, via conflict mediation, requires the reorganization
of the basic components of fitness (survival and reproduction) and
life-properties (such as immortality and totipotency) as well as the co-option
of lower-level processes for new functions at the higher level. The way in
which the conflicts associated with the transition in individuality have been
mediated, and fitness and general life-traits have been re-organized, can
influence the potential for further evolution (i.e., evolvability) of the newly
emerged evolutionary individual. We use the volvocalean green algal group as a model-system
to understand evolutionary transitions in individuality and to apply and test
the theoretical principles presented above. Lastly, we discuss how the
different notions of individuality stem from the basic properties of fitness in
a multilevel selection context.
Kirk DL
Seeking the
ultimate and proximate causes of Volvox
multicellularity and cellular differentiation
INTEGR COMP BIOL 43 (2): 247-253 APR 2003
Abstract:
Volvox and its relatives
provide an exceptional model for integrative studies of the evolution of
multicellularity and cellular differentiation. The volvocine algae range in
complexity from unicellular Chlamydomonas through several colonial genera with
a single cell type, to multicellular Volvox with its germsoma division
of labor. Within the monophyletic family Volvocaceae, several species of Volvox
have evolved independently in different lineages, the ultimate cause presumably
being the advantage that large size and cellular differentiation provide in
competing for limiting resources such as phosphorous. The proximate causes of
this type of evolutionary transition are being studied in V carteri. All
volvocine algae except Volvox exhibit biphasic development: cells grow
during a motile, biflagellate phase, then they lose motility and divide
repeatedly during the reproductive phase. In V carteri three kinds of genes
transform this ancestral biphasic program into a dichotomous one that generates
non-motile reproductive cells and biflagellate somatic cells with no
reproductive potential: first the gls genes act in early embryos to cause
asymmetric division and production of large-small sister-cell pairs; then lag
genes act in the large cells to repress the biflagellate half of the ancestral
program, while regA acts in the small cells to repress the reproductive half of
the program. Molecular-genetic analysis of these genes is progressing, as will
be illustrated with regA, which encodes a transcription factor that acts in
somatic cells to repress nuclear genes encoding chloroplast proteins.
Repression of chloroplast biogenesis prevents these obligately photoautotrophic
cells from growing, and since they cannot grow, they cannot reproduce.
Mori T, Kuroiwa H, Higashiyama T, et al.
Identification of
higher plant GlsA, a putative morphogenesis factor of gametic cells
BIOCHEM BIOPH RES CO 306 (2): 564-569
Abstract:
GlsA has been identified in an asexual-reproductive-cell (gonidia)-deficient
mutant of Volvox as a chaperone-like protein essential for gonidia
production. In this study, we isolated an angiosperm glsA (LlglsA) gene expressed
during Lilium longiflorum pollen development. Immunoblot analyses showed that
the strong LlGlsA expression occurred in the generative cell and its pattern
during pollen development corresponded to that of alpha-tubulin. Morphological
analyses succeeded in visualizing the dispersion of the strong LlGlsA signal in
developing generative cells. In addition, multiple-immunofluorescence staining
of LIGNA and alpha-tubulin revealed that some of the dot-like LlGlsA signals
were co-localized with microtubule filaments. From those results, we suggest
that angiosperm GlsA functions as a chaperone modifying various structures
during male gametic cell formation. (C) 2003 Elsevier Science (
Nishii
I, Ogihara S, Kirk DL
A kinesin, InvA,
plays an essential role in Volvox
morphogenesis
CELL 113 (6): 743-753
Abstract:
In Volvox carted adults, reproductive cells called gonidia are enclosed
within a spherical monolayer of biflagellate somatic cells. Embryos must
"invert" (turn inside out) to achieve this configuration, however,
because at the end of cleavage the gonidia are on the outside and the flagellar
ends of all somatic cells point inward. Generation of a bend region adequate to
turn the embryo inside out involves a dramatic change in cell shape, plus cell
movements. Here, we cloned a gene called invA that is essential for inversion
and found that it codes for a kinesin localized in the cytoplasmic bridges that
link all cells to their neighbors. In invA null mutants, cells change shape
normally, but are unable to move relative to the cytoplasmic bridges. A normal
bend region cannot be formed and inversion stops. We conclude that the InvA
kinesin provides the motile force that normally drives inversion to completion.
Bonner
JT
On the origin of
differentiation
J BIOSCIENCES 28 (4): 523-528 JUN 2003
Abstract:
Following the origin of multicellularity in many groups of primitive organisms
there evolved more than one cell type. It has been assumed that this early
differentiation is related to size - the larger the organism the more cell types.
Here two very different kinds of organisms are considered: the volvocine algae
that become multicellular by growth, and the cellular slime moulds that become
multicellular by aggregation. In both cases there are species that have only
one cell type and others that have two. It has been possible to show that there
is a perfect correlation with size: the forms with two cell types are
significantly larger-than those with one. Also in both groups there are forms
of intermediate size that will vary from one to two cell types depending on the
size of the individuals, suggesting a form of quorum sensing. These
observations reinforce the view that size plays a critical role in influencing
the degree of differentiation.
Michod RE, Nedelcu AM, Roze D
Cooperation and
conflict in the evolution of individuality IV. Conflict mediation and
evolvability in Volvox carteri
BIOSYSTEMS 69 (2-3): 95-114 MAY 2003 (for pdf click here)
Abstract:
The continued well being of evolutionary individuals (units of selection and
evolution) depends upon their evolvability, that is their capacity to generate
and evolve adaptations at their level of organization, as well as their longer
term capacity for diversifying into more complex evolutionary forms. During a
transition from a lower- to higher-level individual, such as the transition
between unicellular and multicellular organisms, the evolvability of the
lower-level (cells) must be restricted, while the evolvability of the new
higher-level unit (multicellular organism) must be enhanced. For these reasons,
understanding the factors leading to an evolutionary transition should help us
to understand the factors underlying the emergence of evolvability of a new
evolutionary unit. Cooperation among lower-level units is fundamental to the
origin of new functions in the higher-level unit. Cooperation can produce a new
more complex evolutionary unit, with the requisite properties of heritable
fitness variations, because cooperation trades fitness from a lower-level (the
costs of cooperation) to the higher-level (the benefits for the group). For
this reason, the evolution of cooperative interactions helps us to understand
the origin of new and higher-levels of fitness and organization. As cooperation
creates a new level of fitness, it also creates the opportunity for conflict
between levels of selection, as deleterious mutants with differing effects at
the two levels arise and spread. This conflict can interfere with the
evolvability of the higher-level unit, since the lower and higher-levels of
selection will often "disagree" on what adaptations are most
beneficial to their respective interests. Mediation of this conflict is
essential to the emergence of the new evolutionary unit and to its continued
evolvability. As an example, we consider the transition from unicellular to
multicellular organisms and study the evolution of an early-sequestered germ-line
in terms of its role in mediating conflict between the two levels of selection,
the cell and the cell group. We apply our theoretical framework to the
evolution of germ/soma differentiation in the green algal group Volvocales. In
the most complex member of the group, Volvox carteri, the potential
conflicts among lower-level cells as to the "right" to reproduce the
higher-level individual (i.e. the colony) have been mediated by restricting
immortality and totipotency to the germ-line. However, this mediation, and the
evolution of an early segregated germ-line, was achieved by suppressing mitotic
and differentiation capabilities in all post-embryonic cells. By handicapping
the soma in this way, individuality is ensured, but the solution has affected the
long-term evolvability of this lineage. We think that although conflict
mediation is pivotal to the emergence of individuality at the higher-level, the
way in which the mediation is achieved can greatly affect the longer-term
evolvability of the lineage. (C) 2002 Elsevier Science Ireland Ltd. All rights
reserved.
Laflamme
M, Lee RW
Mitochondrial
genome conformation among CW-group chlorophycean algae
J PHYCOL 39 (1): 213-220 FEB 2003
Abstract:
Most green algal taxa have circular-mapping mitochondrial genomes, whereas some
have linear genome- or subgenomic-sized mitochondrial DNAs (mtDNA). It is not
clear, however, if the circular-mapping genomes represent genome-sized circular
molecules, if such circular molecules and the linear forms are the predominant
in vivo mtDNA structures, or if the linear forms arose only once or multiple
times among extant green algal lineages. We therefore examined the DNA components
detected with homologous mtDNA probes after pulsed-field gel electrophoresis of
total cellular DNA from the chlorophycean basal bodies displaced
clockwise(CW)-group taxa Chlamydomonas reinhardtii and Chlamydomonas moewusii.
For C. reinhardtii , the 15.8-kb linear mtDNA was the only DNA component
detected, and there was no evidence of circular or large linear precursors of
this DNA. In the case of C. moewusii , which is known to have a
circular-mapping 22.9-kb mitochondrial genome, three DNA components were
detected; these appeared to be circular (relaxed and supercoiled) and
genome-sized linear DNA molecules, the latter of which likely resulted from
random double-strand breaks in the circular forms during DNA isolation. In
further studies, DNA from additional CW-group taxa was examined using
conventional gel electrophoresis and DNA-filter blot analysis with C.
reinhardtii and C. moewusii mtDNA probes. We conclude that all taxa from the
"Volvox clade" (sensu Nakayama et al. 1996) of the CW-group
have genome- or subgenomic-sized linear mtDNAs as their predominant mtDNA form
and that these arose from a genome-sized circular form in an ancestor that
existed near the base of this clade.
Hallmann A
Extracellular
matrix and sex-inducing pheromone in Volvox
INT REV CYTOL 227: 131-+ 2003
Schmitt R, Sumper M
Developmental
biology - How to turn inside out
NATURE 424 (6948): 499-500
2002
Desnitski AG
Dormant stages of the green
flagellate in Volvox in a natural habitat
RUSSIAN JURNAL OF DEVELOPMENTAL BIOLOGY 33(2): 107-109; 2002 (for pdf click here)
Coleman AW
Comparison of
Eudorina/Pleodorina ITS sequences of isolates from nature with those from
experimental hybrids
AM J BOT 89 (9): 1523-1530 SEP 2002
Abstract:
Internal transcribed spacer (ITS) regions of nuclear ribosomal repeats were
compared among 50 Eudorina and Pleodorina isolates and two Volvox
species known to clade with Eudorina species. Of the six major subclades found,
four containing Eudorina and Pleodorina illinoisensis isolates, one containing
Eudorina and Pleodorina indica, and one containing Volvox gigas and V.
powersii, the basal branching order remains uncertain, but the positioning of
isolates known to mate was always as nearest neighbors on the terminal branches
of the tree. Four hybrid clones from a cross of E. elegans with P.
illinoisensis, known from chromosome counts to be products of the failure of
meiosis at zygote germination, contain both parental ITS repeat regions, as
expected. However, they have in addition both crossover and other variant ITS
cistrons among their many repeats of ITS. Such variation is limited to terminal
regions of helices, as recognized from knowledge of RNA transcript secondary
structure. Proper alignment then utilizes all of the nucleotide positions; the
hybrid variants appear in positions intermediate between their parents in the
tree. In fact, such variants seem to be hallmarks of recent hybridization
events, since they were not found in any of the other 50 isolates.
Duncan L, Bouckaert K, Yeh F, et al.
Kangaroo, a
mobile element from Volvox
carteri, is a member of a newly recognized third class of retrotransposons
GENETICS 162 (4): 1617-1630 DEC 2002
Abstract:
Retrotransposons play an important role in the evolution of genomic structure
and function. Here we report on the characterization of a novel retrotransposon
called kangaroo front the multicellular green alga, Volvox carteri.
kangaroo elements are highly mobile and their expression is developmentally
regulated. The), probably integrate via double-stranded, closed-circle DNA
intermediates through the action of an encoded recombinase related to the
X-site-specific integrase. Phylogenetic analysis indicates that kangaroo
elements are closely related to other unorthodox retrotransposons including PAT
(from a nematode), DIRS-1 (from Dictyostelium), and DrDIRS1 (from zebrafish).
PAT and kangaroo both contain split direct repeat (SDR) termini, and here we
show that DIRS-1 and DrDIRS1 elements contain terminal features structurally
related to SDRs. Thus, these mobile elements appear to define a third class of
retrotransposons (the DIRS1 group) that are unified by common structural
features, genes, and integration mechanisms, all of which differ from those of
LTR and conventional non-LTR retrotransposons.
Berthold P, Schmitt R, Mages W
An engineered
Streptomyces hygroscopicus aph 7" gene mediates dominant resistance
against hygromycin B in Chlamydomonas reinhardtii
PROTIST 153 (4): 401-412 DEC 2002
Abstract:
We have developed a positively selectable marker for the green alga
Chlamydomonas reinhardtii using the Streptomyces hygroscopicus aminoglycoside
phosphotransferase gene (aph7"). Its expression is controlled by C.
reinhardtii regulatory elements, namely, the beta2-tubulin gene promoter in
combination with the first intron and the 3' untranslated region of the small
subunit of ribulose bisphosphate carboxylase, rbcS2. C. reinhardtii cell-wall
deficient and wild-type strains were transformed at rates up to 5 x 10(-5) with
two constructs, pHyg3 and pHyg4 (intron-less). Transformants selected on plates
with 10 mug/ml hygromycin B exhibited diverse levels of resistance of up to 200
mug/ml that were stably maintained for at least seven months; they contained
two to five copies of the construct integrated in their genomes. Transcription
of the chimeric aph7" gene, correct splicing of the rbcS2 intron, and
polyadenylation of the transcripts have been verified by sequencing of RT-PCR
products. Average co-transformation rates using pHyg3 and a second selectable
plasmid were about 11%. This advocates the hygromycin-resistance plasmid,
pHyg3, as a new versatile tool for the transformation of a broad range of C.
reinhardtii strains without the sustained need for using auxotrophic mutants as
recipients.
Gradmann D, Ehlenbeck S, Hegemann P
Modeling
light-induced currents in the eye of Chlamydomonas reinhardtii
J MEMBRANE BIOL 189 (2): 93-104
Abstract:
Rhodopsin-mediated electrical events in green algae have been recorded in the
past from the eyes of numerous micro-algae like Haematococcus pluvialis, Chlamydomonas
reinhardtii and Volvox carteri. However, the electrical data gathered by
suction-pipette techniques could be interpreted in qualitative terms only. Here
we present two models that allow a quantitative analysis of such results:
First, an electrical analog circuit for the cell in suction pipette
configuration is established. Applying this model to experimental data from
unilluminated cells of C. reinhardtii yields a membrane conductance of about 3
Sm-2. Furthermore, an analog circuit allows the determination of the
photocurrent fraction that is recorded under experimental conditions. Second, a
reaction scheme of a rhodopsin-type photocycle with an early Ca2+ conductance
and a later H+ conductance is presented. The combination of both models provides
good fits to light-induced currents recorded from C. reinhardtii. Finally, it
allowed the calculation of the impact of each model parameter on the time
courses of observable photocurrent and of inferred transmembrane voltage. The
reduction of the flash-to-peak times at increasing. light intensities are
explained by superposition of two kinetically distinct rhodopsins and by
assuming that the Ca2+-conducting state decays faster at more positive membrane
voltages.
Saliu JK
The diet of
Brycinus nurse (Pisces : Characidae) from Asa Reservoir, Ilorin, Nigeria
REV BIOL TROP 50 (1): 239-243 MAR 2002
Abstract:
From November 1991 to October 1993, 980 specimens of the characid Brycinus
nurse were collected from Asa reservoir to examine its diet. The diet was
analyzed using the frequency of occurrence, numerical and gravimetric methods.
Two hundred and sixty nine (27.45%) of the stomachs examined were empty. The fish
was an omnivore feeding extensively on a wide array of plant and animal food
items. These consisted of 9 families, 10 genera and 10 species. The most
extensively consumed plant food item was aquatic plant parts which occurred in
63.88% of the stomachs, and accounted for 6.06% by number and 12.10% by weight
while the ephemeropteran, Povilla adusta was the most dominant animal food
item, occurring in 50.92% of the stomachs, and accounting for 11.98% by number
and 11.86% by weight. Conversely, the least consumed plant food item was Volvox
occurring in 4.49% of the stomachs and accounting for 0.18% by number and 0.35%
by weight, while the fish Barbus sp. was the least consumed animal food item
occurring in 0.51% of the stomachs, accounting for 0.03% by number and 1.62% by
weight. New food items not previously recorded such as a watermite, Aspatharia
sinuata and Barbus callipterus were found in the stomach contents. The
nonspecific feeding regime of the fish and its ability to utilize different
food items effectively was what accounted for the prominence and wide
distribution of the fish in the lake.
Heitzer M, Hallmann A
An
extracellular matrix-localized metalloproteinase with an exceptional QEXXH
metal binding site prefers copper for catalytic activity
J BIOL CHEM 277 (31): 28280-28286
Abstract:
The extracellular matrix (ECM) of the simple multicellular organism Volvox
contains many region-specific morphological elements and mediates a variety of
developmental and physiological responses by modification of its components.
The fact that >95% of the mature organism is ECM makes Volvox
suitable as a model system for ECM investigations. VMPs are a family of Volvox
genes that are homologous to zinc-dependent matrix metalloproteinases (MMPs).
Here we describe the identification and purification of the first VMP protein,
VMP3. The 470-kDa VMP3 glycoprotein is localized within the ECM, and its
biosynthesis is induced by the sex pheromone. The metal binding motif of VMP3
is QEXXH, not HEXXH as known for 1300 other metalloproteinases. VMP3 shows
proteinase activity and is inhibited by EDTA or the MMP inhibitor GM 6001, but
in contrast to all known proteinases, VMP3 clearly prefers copper for activity
rather than zinc. The exchange from Q to H within the QEXXH motif abolishes its
copper preference. The unique properties of VMP3 suggest a novel type of
metalloproteinase.
Nozaki H, Takahara M, Nakazawa A, et al.
Evolution of
rbcL group IA introns and intron open reading frames within the colonial
Volvocales (Chlorophyceae)
MOL PHYLOGENET EVOL 23 (3): 326-338 JUN 2002
Abstract:
Aono N, Shimizu T, Inoue T, et al.
Palindromic
repetitive elements in the mitochondrial genome of Volvox
FEBS LETT 521 (1-3): 95-99
Abstract:
Group I introns were found in the cob and cox I genes of Volvox carteri.
These introns contain tandem arrays of short palindromic sequences that are
related to each other. Inspection of other regions in the mtDNA revealed that
similar palindromic repetitive sequences are dispersed in the non-protein
coding regions of the mitochondrial genome. Analysis of the group I intron in
the cob gene of another member of Volvocaceae, Volvox aureus, has shown
that its sequence is highly homologous to its counterpart in V. carteri with
the exception of a cluster of palindromic sequences not found in V. carteri.
This indicates that the palindromic clusters were inserted into the introns
after divergence of the two species, presumably due to frequent insertions of
the palindromic elements during evolution of the Volvocaceae. Possible involvement
of the palindromic repetitive elements in the molecular evolution of functional
RNAs is discussed. (C) 2002 Published by Elsevier Science B.V. on behalf of the
Federation of European Biochemical Societies.
Ender F, Godl K, Wenzl S, et al.
Evidence for
autocatalytic cross-linking of hydroxyproline-rich glycoproteins during
extracellular matrix assembly in volvox
PLANT CELL 14 (5): 1147-1160 MAY 2002
Abstract:
The alga Volvox carteri is one of the simplest multicellular organisms,
yet it has a surprisingly complex extracellular matrix (ECM), making Volvox
suitable as a model system in which to study ECM self-assembly. Here, we
analyze the primary structures and post-translational modifications of two main
ECM components synthesized in response to sexual induction as well as wounding.
These proteins are members of the pherophorin family with as yet unknown
properties. They contain polyhydroxyproline spacers as long as 500 and 2750
residues. Even the highly purified proteins retain the capacity to
self-assemble and cross-link, producing an insoluble fibrous network in an
apparently autocatalytic reaction. This pherophorin-based network is located within
the deep zone of the ECM. A molecular genetic search for additional members of
the pherophorin family indicates that at least nine different pherophorin
species can be expected to serve as precursors for ECM substructures.
Therefore, the highly diversified members of the pherophorin family represent
region-specific morphological building blocks for ECM assembly and
cross-linking.
Shimizu T, Inoue T, Shiraishi H
Cloning and
characterization of novel extensin-like cDNAs that are expressed during late
somatic cell phase in the green alga Volvox
carteri
GENE 284 (1-2): 179-187 FEB 6 2002
Abstract:
Asexual individuals of the green alga Volvox carteri consist of two cell
types, somatic and reproductive cells. The somatic cells are terminally
differentiated post-mitotic cells which undergo gradual senescence leading to
cell death in every generation. To understand the gene expression programs associated
with senescence of somatic cells, we cloned two cDNAs, LSG1 and LSG2, that are
preferentially expressed during this late developmental stage. These two cDNAs
were deduced to encode Pro-rich motifs characteristic of extensin proteins that
are components of the extracellular in matrix. LSG1 also resembled genes
encoding plant pathogenesis-related protein 1 (PR-1), while LSG2 showed
similarities with genes encoding matrix metalloproteinases, including a gamete
lytic enzyme of Chlamydomonas. We also found that S9, one of the late somatic
cDNAs previously cloned by Tam and Kirk (Dev. Biol. 145 (1991) 51), was deduced
to encode a protein with a composition similar to LSG2. The expression of PR-1
and a matrix-metalloproteinase-encoding gene has been shown to be induced
during senescence in higher plants. These results indicate that some of the
late somatic genes in V. carteri are related to the senescence-associated genes
in higher plants. (C) 2002 Elsevier Science B.V. All rights reserved.
Miller SM
Taming the
fierce roller: an "enhanced" understanding of cellular
differentiation in Volvox
BIOESSAYS 24 (1): 3-7 JAN 2002
Abstract:
Few organisms offer a better opportunity to explore the mechanisms of cellular
differentiation, and their origins, than Volvox. Volvox consists
of just two cell types, germ and soma, and is the most complex member of a
family of green algae that includes unicellular and multicellular relatives. At
the heart of the cell-fate determination program of Volvox carted is the
regA gene, which encodes a putative transcriptional repressor that prevents
somatic cells from expressing reproductive functions. Stark et al.((1)) have
dissected the regA gene to determine how its expression is restricted to
somatic cells. Their results suggest that regrA expression is controlled by
multiple enhancers, the most important of which prevents transcription in
reproductive cells. While these findings shed light on Volvox
development, they also raise a new set of questions about the mechanisms that
control the germ-soma dichotomy in this organism. (C) 2002 John Wiley Sons,
Inc.
Nishii I, Kirk DL
A
kinesin-like protein encoding gene, invA, is required for the cellular
movements that drive inversion of Volvox
embryos
MOL BIOL CELL 13: 834 NOV 2002
Stark K, Schmitt R
Genetic
control of germ-soma differentiation in Volvox
carteri
PROTIST 153 (2): 99-107 JUN 2002
2001
Kirk DL, Nishii I
Volvox carteri as a model for studying the genetic and
cytological control of morphogenesis
DEV GROWTH DIFFER 43 (6): 621-631 DEC 2001
Abstract:
The green alga Volvox carteri has a very simple and regular adult form
that arises through a short sequence of well-defined morphogenetic steps. A
mature gonidium (asexual reproductive cell) initiates a stereotyped sequence of
rapid cleavage divisions that will produce all of the cells found later in an
adult. A predictable subset of these divisions are asymmetric and result in
production of a small set of germ cells in a precise spatial pattern.
Throughout cleavage, all intracellular components are held in predictable
spatial relationships by a cytoskeleton of unusually regular structure, while
neighboring cells are also held in fixed spatial relationships by an extensive
network of cytoplasmic bridges that form as a result of incomplete cytokinesis.
As a result of these two orienting mechanisms combined, dividing cells are
arranged around the anterior-posterior axis of the embryo with precise
rotational symmetry. These relationships are maintained by the cytoplasmic
bridge system when the embryo that was inside out at the end of cleavage turns
right-side out in the gastrulation-like process of inversion. Inversion is
driven by a cytoskeleton-mediated sequence of cell shape changes, cellular
movements and coordinated contraction. Then, by the time the cytoplasmic
bridges begin to break down shortly after inversion, a preliminary framework of
extracellular matrix (ECM) has been formed. The ECM traps the cells and holds
them in the rotational relationships that were established during cleavage, and
that must be maintained in order for the adult to be able to swim. Transposon
tagging is now being used to clone and characterize the genes regulating these
morphogenetic processes.
Sineshchekov OA, Govorunova EG
Rhodopsin
receptors of phototaxis in green flagellate algae
BIOCHEMISTRY-MOSCOW+ 66 (11): 1300-1310 NOV 2001
Abstract:
Green flagellate algae are capable of the active adjustment of their swimming
path according to the light direction (phototaxis). This direction is detected
by a special photoreceptor apparatus consisting of the photoreceptor membrane
and eyespot. Receptor photoexcitation in green flagellates triggers a cascade
of rapid electrical events in the cell membrane which plays a crucial role in
the signal transduction chain of phototaxis and the photophobic response. The
photoreceptor current is the earliest so far detectable process in this
cascade. Measurement of the photoreceptor current is at present the most
suitable approach to investigation of the photoreceptor pigment in green flagellate
algae, since a low receptor concentration in the cell makes application of
optical and biochemical methods so far impossible. A set of physiological
evidences shows that the phototaxis receptor in green flagellate algae is a
unique rhodopsin-type protein. It shares common chromophore properties with
retinal proteins from archaea. However, the involvement of photoelectric
processes in the signal transduction chain relates it to animal visual
rhodopsins. The presence of some enzymatic components of the animal visual
cascade in isolated eyespot preparations might also point to this relation. A
retinal-binding protein has been identified in such preparations, the amino
acid sequence of which shows a certain homology to sequences of animal visual
rhodopsins. However, potential function of this protein as the phototaxis
receptor has been questioned in recent time.
Kaiser D
Building a
multicellular organism
ANNU REV GENET 35: 103-123 2001
Abstract:
Multicellular organisms appear to have arisen from unicells numerous times.
Multicellular cyanobacteria arose early in the history of life on Earth.
Multicellular forms have since arisen independently in each of the kingdoms and
several times in some phyla. If the step from unicellular to multicellular life
was taken early and frequently, the selective advantage of multicellularity may
be large. By comparing the properties of a multicellular organism with those of
its putative unicellular ancestor, it may be possible to identify the selective
force(s). The independent instances of multicellularity reviewed indicate that
advantages in feeding and in dispersion are common. The capacity for signaling
between cells accompanies the evolution of multicellularity with cell
differentiation.
Fuhrmann M, Stahlberg A, Govorunova E, et al.
The abundant
retinal protein of the Chlamydomonas eye is not the photoreceptor for
phototaxis and photophobic responses
J CELL SCI 114 (21): 3857-3863 NOV 2001
Abstract:
The chlamyopsin gene (cop) encodes the most abundant eyespot protein in the
unicellular green alga Chlamydomonas reinhardtii. This opsin-related protein
(COP) binds retinal and was thought to be the photoreceptor controlling
photomovement responses via a set of photoreceptor currents. Unfortunately,
opsin-deficient mutants are not available and targeted disruption of non-selectable
nuclear genes is not yet possible in any green alga. Here we show that
intron-containing gene fragments directly linked to their intron-less antisense
counterpart provide efficient post-transcriptional gene silencing (PTGS) in C.
reinhardtii, thus allowing an efficient reduction of a specific gene product in
a green alga. In opsin-deprived transformants, Hash-induced photoreceptor
currents (PC) are left unchanged. Moreover, photophobic responses as studied by
motion analysis and phototaxis tested in a light-scattering assay were
indistinguishable from the responses of untransformed wild-type cells. We
conclude that phototaxis and photophobic responses in C. reinhardtii are
triggered by an as yet unidentified rhodopsin species.
Kirk DL
Germ-soma
differentiation in Volvox
DEV BIOL 238 (2): 213-223
Abstract:
Volvox carteri is a spherical green alga with a predominantly asexual mode
of reproduction and a complete germ-soma division of labor. Its somatic cells
are specialized for motility, incapable of dividing, and pro-rammed to die when
only a few days old, whereas its gonidia (asexual reproductive cells) are
nonmotile, specialized for growth and reproduction, and potentially immortal.
When a gonidium is less than 2 days old it divides to produce a juvenile
spheroid containing all of the somatic cells and gonidia that will be present
in an adult of the next generation. The first visible step in germ-soma
differentiation is a set of asymmetric cleavage divisions in the embryo that
set apart small somatic initials from their large gonidial-initial sister
cells. Three types of genes have been found to play key roles in germ-soma specification.
First a set of gls genes act in the embryos to shift cell-division planes,
resulting in the asymmetric divisions that set apart the large-small
sister-cell pairs. Then a set of lag genes act in the large cells to prevent
somatic differentiation, while the regA gene acts in the small cells to prevent
reproductive development. An inducible transposon was used to tag and recover
some of these and other developmentally important genes. The glsA gene encodes
a chaperone-like protein that, like another chaperone that is one of its
putative binding partners, is associated with the cell division apparatus,
although how this leads to asymmetric division remains to be elucidated. The
regA gene encodes a somatic-cell-specific nuclear protein that appears to function
by repressing genes required for chloroplast biogenesis, thereby preventing
somatic cells from growing enough to reproduce. Somatic-cell-specific
expression of regA is controlled by three intronic enhancers. (C) 2001 Academic
Press.
A
senescence-associated S-like RNase in the multicellular green alga Volvox carteri
GENE 274 (1-2): 227-235
Abstract:
Asexual individuals of the green alga Volvox carteri consist of only two
cell types. somatic and reproductive cells. The somatic cells are terminally
differentiated, post-mitotic cells which undergo gradual senescence leading to
cell death in every generation. To elucidate the self-degrading process of
macromolecules associated with senescence, we attempted to clone an RNase whose
mRNA accumulation is increased during senescence. The corresponding cDNA clone
VRN1, encoding an S-like RNase of V. carteri, is the first T-2/S-like RNase to
be cloned from green algae. Semi-quantitative RT-PCR analysis revealed that a
relative amount of VPN1 mRNA is more than three-fold higher in the senescent
somatic cells than in young somatic cells when the mRNA of ribosomal protein S18
is used as an internal standard. VRN1 mRNA is not induced by phosphate
starvation, indicating that its accumulation during senescence is not due to a
self-induced defect in utilizing phosphates. Similar regulation has been
reported for RNS3, which encodes the S-like RNase that is induced in senescent
leaves of Arabidopsis thaliana. These observations imply that VRN1 may promote
RNA degradation during senescence of somatic cells in V. carteri, and that its
regulation has similarity with that of certain senescence-associated RNases in
higher plants. (C) 2001 Elsevier Science B.V. All rights reserved.
Hallmann A, Amon P, Godl K, et al.
Transcriptional
activation by the sexual pheromone and wounding: a new gene family from Volvox encoding modular proteins with
(hydroxy)proline-rich and metalloproteinase homology domains
PLANT J 26 (6): 583-593 JUN 2001
Abstract:
The green alga Volvox represents the simplest kind of multicellular
organism: it is composed of only two cell types, somatic and reproductive,
making it suitable as a model system. The sexual development of males and
females of Volvox carteri is triggered by a sex-inducing pheromone at a
concentration of < 10(-16) M. Early biochemical responses to the pheromone
involve structural modifications within the extracellular matrix (ECM). By
differential screenings of cDNA libraries made from mRNAs of pheromone-treated Volvox,
four novel genes were identified that encode four closely related Volvox
metalloproteinases that we use to define a new protein family, the VMPs. The
existence of several features common to matrix glycoproteins, such as signal
peptides, a (hydroxy)proline content of 12-25%, and Ser(Pro)(2-4) repeats,
suggest an extracellular localization of the VMPs within the ECM. Synthesis of
VMP cDNAs is triggered not only by the sex-inducing pheromone, but also by
wounding, and is restricted to the somatic cell type. Sequence comparisons
suggest that the VMPs are members of the MB clan of zinc-dependent matrix
metalloproteinases, although the putative zinc binding site of all VMPs is
QEXXHXXGXXH rather than HEXXHXXGXXH. The presence of glutamine instead of
histidine in the zinc binding motif suggests a novel family, or even clan, of
peptidases. Like the matrixin family of human collagenases, Volvox VMPs
exhibit a modular structure: they possess a metalloproteinase homology domain
and a (hydroxy)proline-rich domain, and one of them, VMP4, also has two additional
domains. Metalloproteinases seem to be crucial for biochemical modifications of
the ECM during development or after wounding in the lower eukaryote Volvox
with only two cell types, just as in higher organisms.
Kaczanowski S, Jerzmanowski A
Evolutionary
correlation between linker histones and microtubular structures
J MOL EVOL 53 (1): 19-30 JUL 2001
Abstract:
Histones of the H1 group (linker histones) are abundant components of chromatin
in eukaryotes, occurring on average at one molecule per nucleosome. The recent
reports on the lack of a clear phenotypic effect of knock-out mutations as well
as overexpression of histone H1 genes in different organisms have seriously
undermined the long-held view that linker histones are essential for the basic
functions of eukaryotic cells. In an attempt to resolve the paradox of an
abundant conserved protein without a clear function, we re-examined the
molecular and phylogenetic data on linker histones to see if they could reveal
any correlation between the features of H1 and the functional or morphological
characteristics of cells or organisms. Because of an earlier demonstration that
in sea urchin the chromatin-type histone HI is also found in the flagellar
microtubules (Multigner et al. 1992), we focused on the correlation between the
features of H1 and those of microtubular structures. A phylogenetic tree based
on multiple alignment of over 100 available H1 sequences suggests that the
first divergence of the globular domain of H1 (GH1) resulted in branching into
separate types characteristic for plants/Dictyostelium and for
animals/ascomycetes, respectively. The GH1s of these two types differ by a
short region (usually 5 amino acids) placed at a specific location within the
C-terminal wing subdomain of GH1. Evolutionary analysis of the diversification
of H1 mRNA into cell-cycle-dependent (polyA(-)) and independent (polyA(+))
forms showed a mosaic occurrence of these two forms in plants and animals,
despite the fact that the H1 proteins of plants and animals belong to two
well-distinguished groups. However, among organisms from both animal and plant
kingdom, only those with H1 mRNA of a polyA- type have flagellated gametes.
This correlation as well as the demonstration that in Volvox carteri the
accumulation of polyA- mRNA of H1 occurs concurrently with the production of
new flagella (Lindauer et al. 1993), suggests a direct link between polyA-
phenotype of histone H1 mRNA and flagello-genesis.
Stark K, Kirk DL, Schmitt R
Two enhancers
and one silencer located in the introns of regA control somatic cell
differentiation in Volvox
carteri
GENE DEV 15 (11): 1449-1460
Abstract:
The regA gene plays a central role in germ-soma differentiation of Volvox
carteri by suppressing all reproductive functions in somatic cells. Here we
show that the minimal promoter of regA consists of only 42 bp immediately
upstream of the transcription start site, and that it contains no discernible
regulatory elements. However, introns 3 and 5 are both required for regA
expression in somatic cells, and intron 7 is essential for silencing regA in
gonidia (asexual reproductive cells). A regA gene lacking intron 7 rescues the
normal phenotype of mutant somatic cells, but also results in gonidia that
reproduce only weakly and soon die out. The same phenotype is observed when a
regA gene containing intron 7 is placed under control of a constitutive
promoter, suggesting that the silencing activity of intron 7 is promoter
specific. Intron 7 is unusual in that it contains a potential
Babinger P, Kobl I, Mages W, et al.
A link
between DNA methylation and epigenetic silencing in transgenic Volvox carteri
NUCLEIC ACIDS RES 29 (6): 1261-1271
Abstract:
Epigenetic silencing of foreign genes introduced into plants poses an unsolved
problem for transgenic technology. Here we have used the simple multicellular
green alga Volvox carteri as a model to analyse the relation of DNA
methylation to transgenic silencing. Volvox DNA contains on average 1.1%
Ei-methylcytosine and 0.3% N6-methyladenine, as revealed by electrospray mass
spectrometry and phosphoimaging of chromatographically separated P-32-labelled
nucleotides. In two nuclear transformants of V.carteri, produced in 1993 by
biolistic bombardment with a foreign arylsulphatase gene (C-ars), the transgene
is still expressed in one (Hill 181), but not in the other (Hill 183), after an
estimated 500-1000 generations. Each transformant clone contains multiple
intact copies of C-ars, most of them integrated into the genome as tandem
repeats. When the bisulphite genomic sequencing protocol was applied to examine
two select regions of transgenic C-ars, we found that the inactivated copies
(Hill 183) exhibited a high-level methylation (40%) of CpG dinucleotides,
whereas the active copies (Hill 181) displayed low-level (7%) CpG methylation.
These are average values from 40 PCR clones sequenced from each DNA strand in
the two portions of C-ars. The observed correlation of CpG methylation and
transgene inactivation in a green alga will be discussed in the light of
transcriptional silencing.
Ferris PJ, Woessner JP, Waffenschmidt S, et al.
Glycosylated
polyproline II rods with kinks as a structural motif in plant hydroxyproline-rich
glycoproteins
BIOCHEMISTRY-US 40 (9): 2978-2987
Abstract:
Hydroxyproline-rich glycoproteins (HRGPs) are the major proteinaceous
components of higher plant walls and the predominant components of the cell
wall of the green alga Chlamydomonas reinhardtii. The GPI protein, an HRGP of
the C. reinhardtii wall, is shown to adopt a polyproline II helical
configuration and to carry a complex array of arabinogalactoside residues, many
branched, which are necessary to stabilize the helical conformation. The
deduced GP1 amino acid sequence displays two Ser-Pro-rich domains, one with a
repeating (SP), motif and the other with a repeating (PPSPX)(x) motif. A second
cloned gene a2 also carries the PPSPX repeat, defining a novel gene family in
this lineage. The SP-repeat domains of GP1 form a 100-nm shaft with a flexible
kink 28 nm from the head. The gp1 gene encodes a PPPPPRPPFPANTPM sequence at
the calculated kink position, generating the proposal that this insert
interrupts the PPII helix, with the resultant kink exposing amino acids
necessary for GP1 to bind to partner molecules. It is proposed that similar
kinks in the higher plant HRGPs called extensins may play a comparable role in
wall assembly.
Kirk DL
Seeking the
ultimate and proximate causes of Volvox
multicellularity
AM ZOOL 41 (6): 1493-1493 DEC 2001
Nishii I, Kirk DL
The invA gene
of Volvox encodes a novel
kinesin that is required for inversion of the embryo.
DEV BIOL 235 (1): 115
2000
Desnitski AG
Development and reproduction
of two species of the genus Volvox in a shallow temporary pool
PROTISTOLOGY 1(4): 195-198; 2000 (for pdf click here)
Kirk DL
Volvox as a model system for studying the ontogeny and
phylogeny of multicellularity and cellular differentiation
J PLANT GROWTH REGUL 19 (3): 265-274 SEP 2000
Abstract:
Volvox carteri, a spherical alga with a complete division of labor
between approximately 2000 biflagellate somatic cells and 16 asexual
reproductive cells called gonidia, provides a very attractive system for
analyzing how a molecular-genetic program for cell-autonomous cellular
differentiation may be encoded within a genome. Then, when considered in
combination with a group of closely related "volvocine algae" that
includes unicellular Chlamydomonas plus a series of colonial forms of
increasing cell number and complexity, it also provides an attractive model
system for analyzing how such a program for multicellularity and
cytodifferentiation may have evolved. It is proposed that the following were
some of the key steps in this evolutionary pathway: (1) The Chlamydomonas cell
wall was transformed into an extracellular matrix (ECM) that joined sister
cells into a colonial unit. (2) Larger organisms with more abundant ECM were
favored because of the role the ECM plays in storing limiting nutrients. (3) In
the V. carteri lineage the ancestral biphasic "first biflagellate and then
reproductive" pathway of development bt came converted to a dichotomous
pathway by introduction of two kinds of cell-type-specific negative regulators:
one that blocked growth and reproduction in presumptive somatic cells and one
that blocked somatic development in presumptive gonidia. Progress has been made
in cloning and characterizing genes that are involved in setting apart the two
cell lineages of V. carteri and in subsequently controlling their dichotomous
differentiation. The strengths and weaknesses of V. carteri and its relatives
as a model system for studying the evolution of multicellularity are discussed.
Hallmann A, Kirk DL
The
developmentally regulated ECM glycoprotein ISG plays an essential role in
organizing the ECM and orienting the cells of Volvox
J CELL SCI 113 (24): 4605-4617 DEC 2000
Abstract:
Volvox is one of the simplest multicellular organisms with only two cell
types, yet it has a surprisingly complex extracellular matrix (ECM) containing
many region-specific morphological components, making Volvox suitable as
a model system for ECM investigations. ECM deposition begins shortly after
inversion, which is the process by which the embryo turns itself right-side-out
at the end of embryogenesis. It was previously shown that the gene encoding an
ECM glycoprotein called ISG is transcribed very transiently during inversion.
Here we show that the developmentally controlled ISG accumulates at the bases
of the flagella right after inversion, before any morphologically recognizable
ECM structures have yet developed. Later, ISG is abundant in the 'flagellar
hillocks' that encircle the basal ends of all flagella, and in the adjacent
'boundary zone' that delimits the spheroid. Transgenic Volvox were
generated which express a truncated form of ISG, These transgenics exhibit a
severely disorganized ECM within which the cells are embedded in a highly
chaotic manner that precludes motility, A synthetic version of the C-terminal
decapeptide of ISG has a similar disorganizing effect, but only when it is
applied during or shortly after inversion. We postulate that ISG plays a
critical role in morphogenesis and acts as a key organizer of ECM architecture;
at the very beginning of ECM formation ISG establishes an essential initial
framework that both holds the somatic cells in an adaptive orientation and acts
as the scaffold upon which the rest of the ECM can be properly assembled,
assuring that somatic cells of post-inversion spheroids are held in orientations
and locations that makes adaptive swimming behavior possible.
Goodwin PH, Li J, Jin SM
Evidence for sulfate
derepression of an arylsulfatase gene of Colletotrichum gloeosporioides f. sp
malvae during infection of round-leaved mallow, Malva pusilla
PHYSIOL MOL PLANT P 57 (4): 169-176 OCT 2000
Abstract:
An arylsulfatase gene, cgars, was cloned from Colletotrichum gloeosporioides f.
sp. malvae (Cgm), a hemibiotrophic plant pathogenic fungus that causes
anthlacnose disease of round-leaved mallow (Malva pusilla). The clone of cgars
showed high amino acid sequence identity to ass-1(+), an arylsulfatase gene of
Neurospora crassa. Arylsulfatase genes have been shown to be good reporter
genes for detecting available sulfur levels in a variety of microorganisms.
Expression of cgars was determined by relative RT-PCR, in which gars expression
levels were compared to those of actA, a constitutively expressed actin gene of
Cgm, following coamplification. In culture, expression of gars was found to be
repressed by methionine as has been demonstrated for ars-1(+). In host leaf
tissue, cgars expression was relatively higher than actA during penetration,
similar to actA during biotrophic growth and then progressively lower than actA
during necrotrophic growth. These results show that the availability of host
sulfur differs depending upon the stage of infection. (C) 2000 Academic Press.
Nozaki H, Misawa K, Kajita T, et al.
Origin and
evolution of the colonial Volvocales (Chlorophyceae) as inferred from multiple,
chloroplast gene sequences
MOL PHYLOGENET EVOL 17 (2): 256-268 NOV 2000
Abstract:
A combined data set of DNA sequences (6021 bp) from five protein-coding genes
of the chloroplast genome (rbcL, atpB, psaA, psaB, and psbC genes) were
analyzed for 42 strains representing 30 species of the colonial Volvocales (Volvox
and its relatives) and 5 related species of green algae to deduce robust
phylogenetic relationships within the colonial green flagellates. The 4-celled
family Tetrabaenaceae was robustly resolved as the most basal group within the
colonial Volvocales. The sequence data also suggested that all five volvocacean
genera with 32 or more cells in a vegetative colony (all four of the
anisogamous/oogamous genera, Eudorina, Platydorina, Pleodorina, and Volvox,
plus the isogamous genus Yamagishiella) constituted a large monophyletic group,
in which 2 Pleodorina species were positioned distally to 3 species of Volvox.
Therefore, most of the evolution of the colonial Volvocales appears to
constitute a gradual progression in colonial complexity and in types of sexual
reproduction, as in the traditional volvocine lineage hypothesis, although
reverse evolution must be considered for the origin of certain species of
Pleodorina. Data presented here also provide robust support for a monophyletic
family Goniaceae consisting of two genera: Gonium and Astrephomene. (C) 2000
Academic Press.
Sekimoto H
Intercellular
communication during sexual reproduction of Closterium (Conjugatophyceae)
J PLANT RES 113 (1111): 343-352 SEP 2000
Abstract:
Processes of intercellular communication during sexual reproduction of
conjugating green algae Closterium were reviewed. In the case of Closterium
peracerosum-strigosum-littorale complex, two sex-specific pheromones and their
receptors were involved in sexual reproduction. These pheromones were
glycoproteins and the expression of corresponding genes was critically
regulated by the sex and environmental conditions. In the case of Closterium
ehrenbergii, chemotactic and sexual cell division-inducing activities for
mating-type plus cells were detected and characterized. Although many processes
remain to be elucidated, the present results will be helpful for understanding
not only the mode of sexual reproduction in Closterium but also the variety of
intercellular communication in the plant kingdom especially during sexual
reproduction.
Kerszberg M
The survival
of slow reproducers
J THEOR BIOL 206 (1): 81-89
Abstract:
Multicellularity, and the attendant segregation of the germ line, entails the
loss of reproductive capacity by the soma: in Volvox carteri, less than
1 cell in 100 contributes to the next generation. However, compensatory
advantages are unlikely to be very large (Koufopanou & Bell, 1993. Proc. R.
Soc. Lond. (B) 254, 107-113). Somewhat similarly, sex implies the generation of
males, hence a dramatic reproductive slowdown (Barton & Charlesworth, 1998.
Science 281, 1986-1990); yet, a compensating (two-fold) advantage of sex has
not been found. Here, I try to evaluate the actual cost of maintaining slow
reproductive cycles, namely cycles that necessitate the production of
"dead end" units such as somatic cells or males. In a quantitative
model for the competition of individuals with different, heritable reproductive
rates, this cost turns out to be unexpectedly small, and may even sometimes
become irrelevant. The bases for this are made fairly clear: thus, when all
enjoy high fecundity (e.g. a long reproductive life) the handicap of a slower
reproduction vanishes; alternatively, a slight separation of ecological niches
may be sufficient for survival of slower but otherwise unchanged reproducers;
and finally, inherent to slow reproduction is a low rate of destabilizing
genetic change. These facts are largely independent of the formal model
details, and are supported by direct computer simulations. They give a
quantitative basis for analysing the evolution and prevalence of slow life
cycles. The implications of these findings for the evolution of
multicellularity are briefly discussed. (C) 2000 Academic Press.
Matveev V, Matveeva L, Jones GJ
Relative
impacts of Daphnia grazing and direct stimulation by fish on phytoplankton
abundance in mesocosm communities
FRESHWATER BIOL 44 (3): 375-385 JUL 2000
Abstract:
1. Planktivorous fish were hypothesised to influence the abundance of algal
biomass in lakes by changing zooplankton grazing, affecting zooplankton
nutrient recycling and by direct recycling of nutrients to phytoplankton. The
relative roles of direct fish effects vs. zooplankton grazing were tested in
mesocosm experiments by adding to natural communities large grazing zooplankton
(Daphnia carinata) and small planktivorous fish (mosquitofish or juveniles of
Australian golden perch).
2. The addition of Daphnia to natural communities reduced the numbers of all phytoplankton less than 30 mu m in size, but did not affect total biomass of phytoplankton as large Volvox colonies predominated.
3. The addition of Daphnia also reduced the abundance of some small (Moina, Bosmina, Keratella) and large (adult Boeckella) zooplankton, suggesting competitive interactions within zooplankton.
4. The addition of mosquitofish to communities containing Daphnia further reduced the abundance of some small zooplankton (Moina, Keratella), but increased the numbers of Daphnia and adult Boeckella. In spite of the likely increase in grazing due to Daphnia, the abundance of total phytoplankton and dominant alga Volvox did not decline in the presence of mosquitofish but was maintained at a significantly higher level than in control.
5. The addition of juveniles of golden perch to communities containing Daphnia reduced the abundance of small zooplankton (Moina), increased the abundance of large zooplankton (adult Boeckella) but had no significant effect on Daphnia and total phytoplankton abundance.
6. The results of the present study suggest that some planktivorous fish can promote the growth of phytoplankton in a direct way, probably by recycling nutrients, and even in the presence of large grazers. However, the manifestation of the direct effect of fish can vary with fish species.
Suzuki L, Woessner JP, Uchida H, et al.
Zygote-specific
protein with hydroxyproline-rich glycoprotein domains and lectin-like domains
involved in the assembly of the cell wall of Chlamydomonas reinhardtii
(Chlorophyta)
J PHYCOL 36 (3): 571-583 JUN 2000
Abstract:
The cell wall of Chlamydomonas reinhardtii zygotes, which forms rapidly after
the fusion of wall-free gametes, provides a tractable system for studying the
properties and assembly of hydroxyproline-rich glycoproteins, the major
proteinaceous components of green algal and plant cell walls. We report the
cloning of the zsp2 gene and the analysis of its ZSP-2 product, a 58.9 kDa
poly-peptide that is synthesized exclusively by zygotes, The protein contains
two (SP), repeats, establishing it as a member of the cell wall
hydroxyproline-rich glycoproteins family. It also contains a 4-fold iteration
of an amino acid sequence centered around cysteine residues, a configuration
found in both plant and animal lectins, Furthermore, we report four
observations on pellicle composition and production, First, cell-free
preparations of the pellicle matrix are rich in hydroxyproline, arabinose, and
galactose and contain bundles of very long fibrils, Second, glutathione blocks
pellicle formation and results in the accumulation of long fibrils in the
growth medium. Third, antibody to ZSP-8 also blocks pellicle formation, Fourth,
ZSP-2 immunolocalizes to the boundary between the outer layers of the wall
proper and the pellicle matrix. These observations are consistent with the possibility
that the Cys-rich (glutathione-sensitive) lectin-like domains of ZSP-2 may bind
to sugar residues on the long fibrils and anchor
Sumper M, Nink J, Wenzl S
Self-assembly
and cross-linking of Volvox
extracellular matrix glycoproteins are specifically inhibited by Ellman's
reagent
EUR J BIOCHEM 267 (8): 2334-2339 APR 2000
Abstract:
A major impediment to the biochemical characterization of extracellular
matrices from algae (as well as higher plants) is the extensive covalent
cross-linking that exists in the matrix, rendering most components insoluble
and resistant to conventional extraction procedures. In the multicellular green
alga Volvox, biogenesis of the extracellular matrix (ECM) is initiated
immediately after the process of embryonic inversion. At this stage of
development, the sulfhydryl reagent 5,5'-dithio-bis(2-nitrobenzoic acid), known
as Ellman's reagent, interferes in a highly specific manner with ECM
biogenesis. Treated post-inversion embryos are no longer able to assemble an
intact ECM and consequently dissociate into a suspension of single cells.
Dissociated cells remain viable and continue to secrete ECM proteins into the
growth medium, as documented by the identification of several members of the
pherophorin family. Cross-linked ECM polymers such as sulfated surface
glycoprotein 185 remain in a soluble state. Thus, treatment with Ellman's
reagent opens a simple approach for the isolation and characterization of
otherwise inaccessible monomeric precursors.
Wittstock U, Fischer M, Svendsen I, et al.
Cloning and
characterization of two, cDNAs encoding sulfatases in the Roman snail, Helix
pomatia
IUBMB LIFE 49 (1): 71-76 JAN 2000
Abstract:
The sulfatase from the snail Helix pomatia is widely used for analytical
applications. We have investigated the content of sulfatases in H, pomatia,
using a biochemical and a molecular approach. A 112-kDa protein from the
intestinal juice of H. pomatia comigrated with sulfatase activity when
chromatographed on Sephacryl S300 and concanavalin A-Sepharose. The N-terminal
amino acid sequence of the protein was similar to one of three sulfatase motifs
defined by sequence alignment of known sulfatases, Degenerate primers designed
from the motifs and the N-terminal amino acid sequence obtained were used to
generate PCR fragments and to isolate both a full-length and a 3'-truncated
cDNA encoding H, pomatia sulfatases, designated SULF1 and SULF2, SULF1 consists
of 503 amino acids and shows 53-55% identity to the mammalian arylsulfatase B,
The amino acid sequence deduced from the 878-bp SULF2 cDNA fragment is 55% identical
with SULF1, Both SULF1 and SULF2 contain the cysteine residue conserved in the
active site of many sulfatases, which is known to be posttranslationally
modified into formylglycine in eukaryotic sulfatases, However, the SULF1 and
SULF2 cDNAs do not code for the protein purified. This indicates the presence
of at least three sulfatase genes in H. pomatia.
Kirk DL, Miller SM
Embryonic
polarity, asymmetric division,and cell fate determination in Volvox.
DEV BIOL 222 (1): 24
1999
Meissner M, Stark K, Cresnar B,
et al.
Volvox germline-specific genes that are putative targets of
RegA repression encode chloroplast proteins
CURR GENET 36 (6): 363-370 DEC 1999
Abstract:
In Volvox carteri, regA acts as a master gene to suppress all germ cell
functions in somatic cells. Its product, RegA, has features of a
transcriptional repressor. Here we report cDNA sequences representing 15
nuclear genes with properties expected of RegA targets: they are expressed
strongly in germ cells and in regA(-), but not regA(+), somatic cells. Two of
them encode polypeptides with no recognizable features, but ten (like three
previously sequenced ones) encode chloroplast proteins of known function, and
the remaining three encode putative chloroplast proteins of unknown function.
This suggests that RegA blocks reproductive development in somatic cells by
preventing chloroplast biogenesis, thereby making it impossible for the cells
to grow enough to reproduce
Ender F, Hallmann A, Amon P, et al.
Response to
the sexual pheromone and wounding in the green alga Volvox: Induction of an extracellular glycoprotein consisting
almost exclusively of hydroxyproline
J BIOL CHEM 274 (49): 35023-35028 DEC 3 1999
Abstract:
The extracellular matrix (ECM) of Volvox is modified during development
or in response to external stimuli, like the sex-inducing pheromone. It has
recently been demonstrated that a number of genes triggered by the sex-inducing
pheromone are also inducible by wounding. By differential screening of a cDNA
library, a novel gene was identified that is transcribed in response to the
pheromone. Its gene product was characterized as an ECM glycoprotein with a
striking feature: it exhibits a hydroxyproline content of 68% and therefore is
an extreme member of the family of hydroxyproline-rich glycoproteins (HRGPs),
HRGPs are known as constituents of higher plant ECMs and seem to function as
structural barriers in defense responses. The Volvox HRGP is also found
to be inducible by wounding. This indicates that the wound response scenarios
of higher plants and multicellular green algae may be evolutionary related.
Kirk DL
Evolution of
multicellularity in the volvocine algae
CURR OPIN PLANT BIOL 2 (6): 496-501 DEC 1999
Abstract:
Recent studies reveal that relationships among the volvocine algae are more
complex than was previously believed. Nevertheless, this group still appears to
provide an unrivaled opportunity to analyze an evolutionary pathway leading
from unicellularity (Chlamydomonas) to multicellularity with division of labor
(volvox). Significant progress in this regard was made in the past year
when two genes playing key roles in volvox cellular differentiation were
cloned, and clues were uncovered regarding their mechanisms of action.
Coleman AW
Phylogenetic analysis
of "Volvocacae" for comparative genetic studies
P NATL ACAD SCI USA 96 (24): 13892-13897
Abstract:
Sequence analysis based on multiple isolates representing essentially all
genera and species of the classic family Volvocaeae has clarified their
phylogenetic relationships. Cloned internal transcribed spacer sequences
(ITS-1. and ITS-2, flanking the 5.8S gene of the nuclear ribosomal gene
cistrons) were aligned, guided by ITS transcript secondary structural features,
and subjected to parsimony and neighbor joining distance analysis. Results
confirm the notion of a single common ancestor, and Chlamydomonas reinharditii
alone among all sequenced green unicells is most similar. interbreeding
isolates were nearest neighbors on the evolutionary tree in all cases. Some
taxa, at whatever level, prove to be clades by sequence comparisons, but others
provide striking exceptions. The morphological species Pandorina morum, known
to be widespread and diverse in mating pairs, was found to encompass all of the
isolates of the four species of Volvulina. Platydorina appears to have
originated early and not to fall within the genus Eudorina, with which it can
sometimes be confused by morphology. The four species of Pleodorina appear
variously associated with Eudorina examples. Although the species of Volvox
are each clades, the genus Volvox is not The conclusions confirm and
extend prior, more limited, studies on nuclear SSU and LSU rDNA genes and
plastid-encoded rbcL and atpB. The phylogenetic tree suggests which classical
taxonomic characters are most misleading and provides a framework for molecular
studies of the cell cycle-related and other alterations that have engendered
diversity in both vegetative and sexual colony patterns in this classical
family.
Funke RP, Kovar JL, Logsdon JM, et al.
Nucleus-encoded,
plastid-targeted acetolactate synthase genes in two closely related
chlorophytes, Chlamydomonas reinhardtii and Volvox carteri: phylogenetic origins and recent insertion of
introns
MOL GEN GENET 262 (1): 12-21 AUG 1999
Abstract:
Acetolactate synthase (ALS catalyzes the first committed step in the synthesis
of branched-chain amino acids. In green plants and fungi, ALS is encoded by a
nuclear gene whose product is targeted to plastids (in plants) or to
mitochondria tin fungi). In red algae, the gene is plastid-encoded. We have
determined the complete sequence of nucleus-encoded ALS genes from the green algae
Chlamydomonas reinhardtii and Volvox carteri. Phylogenetic analyses of
the ALS gene family indicate that the ALS genes of green algae and plants are
closely related, sharing a recent common ancestor. Furthermore, although these
genes are clearly of eubacterial origin, a relationship to the ALS genes of red
algae and cyanobacteria (endosymbiotic precursors of plastids) is only weakly
indicated. The algal ALS genes are distinguished from their homologs in higher
plants by the fact that they are interrupted by numerous spliceosomal introns;
plant ALS genes completely lack introns. The restricted phylogenetic
distribution of these introns suggests that they were inserted recently, after
the divergence of these green algae from plants. Two introns in the Volvox
ALS gene, not found in the Chlamydomonas gene, are positioned precisely at
sites which resemble "proto-splice" sequences in the Chlamydomonas
gene.
Kobayashi K, Koyanagi R, Matsumoto M, et al.
Switching
from asexual to sexual reproduction in the planarian Dugesia ryukyuensis:
Bioassay system and basic description of sexualizing process
ZOOL SCI 16 (2): 291-298 APR 1999
Abstract:
An assay system has been established for the sexual induction in the OH strain,
an exclusively fissiparous (asexual) strain, of Dugesia ryukyuensis by feeding
them with sexually matured worms of Bdellocephala brunnea, an exclusively
oviparous (sexual) species. In this assay system, asexual worms gradually
differentiated sexual organs, namely the ovary, testis, genital pore and yolk
gland in this order, and eventually mated and laid cocoons filled with
fertilized eggs. Although the OH strain worms were believed not to have any sexual
organs, a pair of undeveloped ovaries with a few oogonia were detected by an
intensive histological search. Along with the progression of sexualization,
five distinct stages were histologically recognized: In the first stage, the
ovaries became larger enough to be externally apparent; oocytes appeared first
at stage 2; the primordial testes emerged at stage 3; a genital pore opened,
yolk gland primordia developed and spermatocytes appeared at stage 4; and
finally at stage 5 matured spermatozoa and yolk glands were formed.
Hoops HJ,
A test of two
possible mechanisms for phototactic steering in Volvox carteri (Chlorophyceae)
J PHYCOL 35 (3): 539-547 JUN 1999
Abstract:
We tested two competing models that could explain how differential flagellar
activity leads to phototactic turning in spheroids of Volvox carteri f,
weismannia (Powers) Iyengar. In one model, turning results from the flagella of
anterior cells in the lighted and shadowed hemispheres beating at different
frequencies. In a competing model, turning results from a change in beat
direction in these flagella. Both models successfully explain phototactic
steering under constant illumination, but they make different predictions when
colonies are exposed to abrupt changes in light intensity. If turning is due to
control of flagellar beat frequency, both progression and rotation rates will
change in the same direction and with similar magnitudes. If spheroid turning
is due to a change in flagellar beat direction, a decreased rate of progression
will accompany an increased rate of rotation and vice versa. We used
video-microscopy to observe the behavior of positively phototactic V. carteri
spheroids exposed to 10x step-up and step-down stimuli. After a step-up
stimulus, spheroids slow their progression and rotation by equal amounts, No
significant changes are reported in these parameters after the reciprocal step-down
response. These observations are consistent with the variable flagellar
frequency model and inconsistent with the variable flagellar direction model
for phototactic turning. Switching the direction of Light stimulus by 180
degrees results in reorientation of positively phototactic spheroids, The
kinetics of this reorientation did not precisely match the predictions of
either model.
Nishii I, Ogihara S
Actomyosin
contraction of the posterior hemisphere is required for inversion of the Volvox embryo
DEVELOPMENT 126 (10): 2117-2127 MAY 1999
Abstract:
During inversion of a Volvox embryo, a series of cell shape changes
causes the multicellular sheet to bend outward, and propagation of the bend
from the anterior to the posterior pole eventually results in an inside-out
spherical sheet of cells. We use fluorescent and electron microscopy to study
the behavior of the cytoskeleton in cells undergoing shape changes.
Microtubules are aligned parallel to the cell's long axis and become elongated
in the bend. Myosin and actin filaments are arrayed perinuclearly before
inversion. In inversion, actin and myosin are located in a subnuclear position
throughout the uninverted region but this localization is gradually lost
towards the bend. Actomyosin inhibitors cause enlargement of the embryo. The
bend propagation is inhibited halfway and, as a consequence, the posterior
hemisphere remains uninverted. The arrested posterior hemisphere will resume
and complete inversion even in the presence of an actomyosin inhibitor if the
anterior hemisphere is removed microsurgically. We conclude that the principal
role of actomyosin in inversion is to cause a compaction of the posterior
hemisphere; unless the equatorial diameter of the embryo is reduced in this
manner, it is too large to pass through the opening defined by the
already-inverted anterior hemisphere.
Huey RB, Berrigan D, Gilchrist GW, et al.
Testing the
adaptive significance of acclimation: A strong inference approach
AM ZOOL 39 (2): 323-336 APR 1999
Abstract:
Acclimation is a common phenotypic response to environmental change.
Acclimation is often thought to enhance performance and thus to be adaptive.
This view has recently been formalized as the "Beneficial Acclimation
Hypothesis" and predicts that individuals acclimated to one environment
perform better in that environment than do individuals acclimated to a
different environment. Although Beneficial Acclimation is appealing and widely
supported, recent studies with E. coli and Drosophila have challenged its
general validity. Although these challenges could be dismissed as mere
exceptions, they encourage a re-evaluation of the adaptive significance of
acclimation. Our philosophical approach differs from that of most previous
studies of acclimation, in which the prediction derived from a Beneficial
Acclimation perspective (e.g., heat tolerance is positively correlated with
acclimation temperature) is tested against the null hypothesis ("single
hypothesis approach"). Instead, we follow Huey and Berrigan (1996) in
advocating a strong inference approach (sensu Platt, 1964), which recognizes
that Beneficial Acclimation is actually one of a set of competing hypotheses
that make different predictions as to how developmental temperature influences
the thermal sensitivity of adults ("developmental acclimation").
Using this perspective, Huey and Berrigan proposed a factorial experimental
design (3 developmental by 3 adult temperatures) designed to discriminate among
all competing hypotheses. We now derive a formal statistical model (ANOVA with
orthogonal polynomial contrasts) for this experimental design and use it to
evaluate simultaneously the relative impact of each competing hypothesis. We
then apply this model to several case studies (Drosophila, Volvox,
Trichogramma), and we review also a recent study with E. coli. The influence of
Beneficial Acclimation is supported (albeit often weakly) in most cases.
Nevertheless, other hypotheses (especially the Optimal Developmental
Temperature Hypothesis) often have a greater impact. Even so, however,
Beneficial Acclimation usually predicts relative performance at extreme test
temperatures. We conclude that, although rumors of its death are premature,
Beneficial Acclimation cannot be viewed as the dominant expectation, at least
with regard to developmental temperature acclimation. Moreover, our findings
reinforce the view that a strong inference approach provides a more
comprehensive portrait of complex biological responses than do
single-hypothesis approaches.
Hallmann A
Enzymes in
the extracellular matrix of Volvox:
an inducible, calcium-dependent phosphatase with a modular composition
J BIOL CHEM 274 (3): 1691-1697
Abstract:
The volvocine algae provide the unique opportunity for exploring development of
an extracellular matrix. Volvox is the most advanced member of this
family and represents the simplest multicellular organism, with differentiated
cells, a complete division of labor, and a complex extracellular matrix, which
serves structural and enzymatic functions. In Volvox carteri a
glycosylated extracellular phosphatase was identified, which is partially
released from the extracellular matrix into the growth medium. The phosphatase
is synthesized in response to inorganic phosphate starvation and is strictly to
inorganic phosphate starvation and is strictly calcium-dependent. The
metalloenzyme has been purified to homogeneity and characterized. Its gene and
cDNA have been cloned. Comparisons of genomic and cDNA sequences revealed an
extremely intron-rich gene (32 introns), With an apparent molecular mass of 160
kDa the Volvox extracellular phosphatase is the largest phosphatase
cloned, with no sequence similarity to any other phosphatase. This enzyme
exhibits a modular composition. There are two large domains and a small one.
The large domains are highly homologous to each other and therefore most likely
originated from gene duplication and fusion. At least one EF-hand motif for
calcium binding was identified in this extracellular protein Volvox
extracellular phosphatase is the first calcium-dependent extracellular
phosphatase to be cloned.
Rodriguez H, Haring MA, Beck CF
Molecular
characterization of two light-induced, gamete-specific genes from Chlamydomonas
reinhardtii that encode hydroxyproline-rich proteins
MOL GEN GENET 261 (2): 267-274 MAR 1999
Abstract:
Gametic differentiation in Chlamydomonas reinhardtii is a two-step process,
which is controlled by the sequential action of the two extrinsic signals,
nitrogen starvation and blue light. The gamete-specific genes GAS28 and GAS29
are expressed in the late phase of gametogenesis. Their light-induced
expression is restricted to cells that have completed the first, nitrogen
starvation-activated, phase of differentiation. A comparison of the two genes
revealed striking similarities as well as differences. Their most prominent shared
feature is an extended sequence homology of over 90% in their 5'-untranslated
regions, suggesting a role in translational regulation. GAS28 and GAS29 both
encode hydroxyproline-rich proteins (HRGPs) of very similar sizes that exhibit
typical features of volvocalean cell wall constituents. GAS28 shows a high
degree of homology with the Volvox pherophorin gene family, suggesting a
relationship between these genes.
Bischoff F, Molendijk A, Rajendrakumar CSV, et al.
GTP binding
proteins in plants
CELL MOL LIFE SCI 55 (2): 233-256 FEB 1999
Abstract:
GTP-binding proteins are found in all organisms. They are important switches
that cycle between an active and an inactive state, ensuring vectorial flow of
information on the expense of guanosine triphosphate (GTP). In this review, we
discuss current progress in the molecular characterization and functional
analysis of plant genes encoding heterotrimeric and small GTPases. An
up-to-date list in eluding all cloned plant GTPase genes is given and a
systematic classification is proposed.
Kirk MM, Stark K, Miller SM, et al.
regA, a Volvox gene that plays a central role
in germ-soma differentiation, encodes a novel regulatory protein
DEVELOPMENT 126 (4): 639-647 Feb 1999
Abstract:
Volvox has two cell types: mortal somatic cells and immortal germ cells.
Here we describe the transposon-tagging, cloning and characterization of regA,
which plays a central role as a master regulatory gene in Volvox
germsoma differentiation by suppressing reproductive activities in somatic
cells. The 12.5 kb regA transcription unit generates a 6,725 nucleotide mRNA
that appears at the beginning of somatic cell differentiation, and that encodes
a 111 kDa RegA protein that localizes to the nucleus, and has an unusual
abundance of alanine, glutamine and proline, This is a compositional feature shared
by functional domains of many 'active' repressors, These findings are
consistent with the hypothesis that RegA acts in somatic cells to repress
transcription of genes required for growth and reproduction, including 13 genes
whose products are required for chloroplast biogenesis.
Miller SM, Kirk DL
glsA, a Volvox gene required for asymmetric
division and germ cell specification, encodes a chaperone-like protein
DEVELOPMENT 126 (4): 649-658 FEB 1999
Abstract:
The gls genes of Volvox are required for the asymmetric divisions that
set apart cells of the germ and somatic lineages during embryogenesis. Here we used
transposon tagging to clone glsA, and then showed that it is expressed
maximally in asymmetrically dividing embryos, and that it encodes a 748-amino
acid protein with two potential protein-binding domains. Site-directed
mutagenesis of one of these, the J domain (by which Hsp40-class chaperones bind
to and activate specific Hsp70 partners) abolishes the capacity of glsA to
rescue mutants. Based on this and other considerations, including the fact that
the GlsA protein is associated with the mitotic spindle, we discuss how it
might function, in conjunction with an Hsp70-type partner, to shift the
division plane in asymmetrically dividing cells.
Nozaki H, Ohta N, Takano H, et al.
Reexamination
of phylogenetic relationships within the colonial Volvocales (Chlorophyta): An
analysis of atpB and rbcL gene sequences
J PHYCOL 35 (1): 104-112 FEB 1999
Abstract:
The chloroplast-encoded atpB gene was sequenced from 33 strains representing 28
species of the colonial Volvocales (the Volvocaceae and its relatives) to
reexamine phylogenetic relationships as previously deduced by morphological
data and rbcL gene sequence data.1128 base pairs in the coding regions of the
atpB gene were analyzed by MP, NJ, and ML analyses, Although supported with
relatively low bootstrap values (75% and 65% in the NJ and ML analyses,
respectively), three anisogamous/oogamous volvocacean genera-Eudorina,
Pleodorina, and Volvox, excluding the section Volvox(= Euvolvox,
illegitimate name), constituted a large monophyletic group (Eudorina group),
Outside the Eudorina group, a robust Lineage composed of three species of Volvox
sect, Volvox was resolved as in the rbcL gene trees, rejecting the hypothesis
of the previous cladistic analysis based on morphological data that the genus Volvox
is monophyletic, In addition, the NJ and ML trees suggested that Eudorina is a
non-monophyletic genus as inferred from the morphological data and rbcL gene
sequences. Although phylogenetic status of the genus Gonium is ambiguous in the
rbcL gene trees and the paraphyly of this genus is resolved in the cladistic
analysis based on morphological data, the atpB gene sequence data suggest
monophyly of Gonium with relatively low bootstrap values (56-61%) in the NJ and
ML trees. On the basis of the combined sequence data (2256 base pairs) from
atpB and rbcL genes, Gonium was resolved as a robust monophyletic genus in the
NJ and ML trees (with 68-86% bootstrap values), and Eudorina elegans Ehrenberg
represented a paraphyletic species positioned most basally within the Eudorina
group, However, phylogenetic status and relationships of the families of the
colonial Volvocales were still almost ambiguous even in the combined analysis.
Braun FJ, Hegemann P
Two
light-activated conductances in the eye of the green alga Volvox carteri
BIOPHYS J 76 (3): 1668-1678 MAR 1999
Abstract:
Photoreceptor currents of the multicellular green alga Volvox carteri
were analyzed using a dissolver mutant. The photocurrents are restricted to the
eyespot region of somatic cells. Photocurrents are detectable from intact cells
and excised eyes. The rhodopsin action spectrum suggests that the currents are
induced by Volvox rhodopsin. Flash-induced photocurrents are a
composition of a fast Ca2+-carried current (P-F) and a slower current (P-S),
which is carried by H+. P-F is a high-intensity response that appears with a
delay of less than 50 mu s after flash. The stimulus-response curve of its
initial rise is fit by a single exponential and parallels the rhodopsin
bleaching. These two observations suggest that the responsible channel is
closely connected to the rhodopsin, both forming a tight complex. At low flash
energies P-S is dominating. The current delay increases up to 10 ms, and the
P-S amplitude saturates when only a few percent of the rhodopsin is bleached.
The data are in favor of a second signaling system, which includes a signal
transducer mediating between rhodopsin and the channel. We present a model of
how different modes of signal transduction are accomplished in this alga under
different light conditions.
Hallmann A, Rappel A
Genetic
engineering of the multicellular green alga Volvox: a modified and multiplied bacterial antibiotic resistance
gene as a dominant selectable marker
PLANT J 17 (1): 99-109 JAN 1999
Abstract:
The green alga Volvox represents the simplest multicellular organism: Volvox
is composed of only two cell types, somatic and reproductive. Volvox,
therefore, is an attractive model system for studying various aspects of
multicellularity. With the biolistic nuclear transformation of Volvox
carteri, the powerful molecular genetic manipulation of this organism has been
established, but applications have been restricted to an auxotrophic mutant
serving as the DNA recipient. Therefore, a dominant selectable marker working
in all strains and mutants of this organism is required. Among several gene
constructs tested, the most advantageous results were obtained with a chimeric
gene composed of the coding sequence of the bacterial ble gene, conferring
resistance to the antibiotic zeocin, modified with insertions of two endogenous
introns from the Volvox arylsulfatase gene and fused to 5' and 3'
untranslated regions from the Volvox beta 2-tubulin gene. In the most
suitable plasmid used, the gene dosage was increased 16-fold by a technique
that allows exponential multiplication of a DNA fragment. Go-transformation of
this plasmid and a non-selectable plasmid allowed the identification of zeocin
resistant transformants with nuclear integration of both selectable and
non-selectable plasmids. Stable expression of the ble gene and of genes from
several non-selectable plasmids is demonstrated. The modified ble gene provides
the first dominant marker for transformation of both wild-type and mutant
strains of Volvox.
Fabry S, Kohler A, Coleman AW
Intraspecies
analysis: Comparison of ITS sequence data and gene intron sequence data with breeding
data for a worldwide collection of Gonium pectorale
J MOL EVOL 48 (1): 94-101 JAN 1999
Abstract:
The morphologically uniform species Gonium pectorale is a colonial green
flagellate of worldwide distribution. The affinities of 25 isolates from 18 sites
on five continents were assessed by both DNA sequence comparisons and sexual
compatibility. Complete sequences were obtained (i) for the internal
transcribed spacer ITS-1 and ITS-2 regions of ribosomal DNA and (ii) for each
of three single-copy spliceosomal introns, two in a small G protein and one in
the actin gene. ITS sequences appeared to homogenize sufficiently rapidly to
behave as a single copy gene. Intron sequence differences between isolates in
this species reached nucleotide substitution saturation, while ITS sequences
did not. Parsimony and evolutionary distance analysis of the two types of DNA
data gave essentially the same tree conformation. By all these criteria, the
group of G. pectorale isolates fell into two main clades, A and B. Clade A,
with isolates from four continents, was comprised of four subclades of quite
closely related isolates, plus one strain of ambiguous affinity. Clade B was
comprised of two subclades represented by South African and South American
isolates, respectively; thus, only subclades of clade B showed geographical
localization. With respect to mating, all isolates except one homothallic
strain and one apparently sterile strain fell into either one or the other of
two mating types. Pairings in all possible combinations revealed that isolates
from the same site formed abundant zygotes, which germinated to produce new,
sexually active organisms. Zygotes were also formed in many pairings of other
combinations, including crosses of clade A with clade B organisms, but none of
the latter produced viable germlings. The ability to mate and produce viable
progeny that were themselves capable of sexual reproduction was restricted to
members of subclades established on the basis of DNA sequence similarities.
Thus, the grades of difference in both nuclear intron sequences and rDNA ITS
sequences paralleled those observed in the sexual analysis.
Miller SM, Kirk DL
glsA, a Volvox gene required for asymmetric
division and germ cell specification, encode a chaperone-like protein that
co-localizes with the mitotic spindle
MOL BIOL CELL 10: 2265 Suppl. S NOV 1999
1998
Gonzalez MA, Gomez PI, Montoya R
Comparison of
PCR-RFLP analysis of the ITS region with morphological criteria of various
strains of Dunaliella
J APPL PHYCOL 10 (6): 573-580 1998
Abstract:
The genus Dunaliella comprises 28 species defined primarily by morphological
and physiological criteria, which vary considerably depending on growth
conditions. Concomitantly, the taxonomic status of various species is
uncertain. To confirm the taxonomic identity and to better understand the
relationship within Dunaliella, seven taxa (D. salina, D. bardawil, D.
tertiolecta, D. parva, D. viridis, D. lateralis, D. peircei) were compared
using RFLP analysis of the nuclear rDNA repeats, specifically the internal
transcribed spacer regions, including the 5.8S rRNA gene. Volvox aureus
was used as an outgroup. A single ITS PCR amplification product was obtained
for each taxon. An ITS fragment of ca. 640 bp was present in all the taxa
within the subgenus Dunaliella, except for D. salina CCMP 1303 (ca. 540 bp) and
D. lateralis (subgenus Pascheria) (ca. 600 bp). A cluster analysis based on the
presence or absence of bands generated by digestion of the PCR product with 8
restriction endonucleases (DpnI, HhaI, EcoRI, PVuII, TaqI, HaeIII, MspI, StyI)
revealed no correlation between the genetic relationship inferred from the
ITS-RFLP data and the morpho-physiological attributes used for taxonomy. In
addition, differences in morphology, physiology and in the length and restriction
fragment patterns of the ITS region of D. salina CCMP 1303 suggest that this
strain does not belong to Dunaliella.
Kobl I, Kirk DL, Schmitt R
Quantitative PCR data falsify the chromosomal
endoreduplication hypothesis for Volvox
carteri (Volvocales, Chlorophyta)
J PHYCOL 34 (6): 981-988
DEC 1998
Abstract:
Two conflicting hypotheses for chromosome replication in the Volvocaceae, one
postulating multiple rounds of replication prior to cell division
(endoreduplication) and the other claiming a canonical sequence of one round of
nuclear DNA replication preceding each cell division, have been tested
experimentally. Competitive PCR of the single-copy actin gene (target) of Volvox
carteri f. nagariensis Iyengar and a shortened gene version (competitor)
containing the same primer binding sites were used to assess the genome
equivalents present in a given number of cells. Determining the molar ratio of
the PCR products generated from target DNA (extracted from a known number of
cells) acid defined numbers of competitor molecules revealed that Volvox
embryos between the one- and 16-cell stages possess an average of between one
and two-but never more than two-copies of the actin gene. This led us to
conclude that the number of genome equivalents per nucleus in dividing Volvox
embryos varies only between one and two and that, unlike the case predicted by
endoredduplication, the nuclear genome undergoes only one round of replication
prior to each cell division.
Sekimoto H, Fukumoto R, Dohmae N, et al.
Molecular
cloning of a novel sex pheromone responsible for the release of a different sex
pheromone in Closterium peracerosum-strigosum-littorale complex
PLANT CELL PHYSIOL 39 (11): 1169-1175 NOV 1998
Abstract:
A sex pheromone, protoplast-release-inducing protein (PR-IP) inducer, of the
Closterium peracerosum-strigosum-littorale complex is known to induce the
release of PR-IF, from mating-type plus (mtf) cells during sexual reproduction.
The purified PR-IF inducer was treated with trypsin to obtain internal peptides
for determination of partial amino acid sequences. Using these sequences,
oligonucleotides were synthesized and used as primers for the combined reverse
transcription-PCR, A 296 bp cDNA fragment was amplified, permitting the cloning
of corresponding full length cDNA (CpPI; Closterium peracerosum-strigosum-littorale
complex PR-IF inducer). The deduced amino acid sequence of CpPI encodes a
protein of 212 amino acid residues of M-r 23,071 whereas portion of the peptide
secreted is predicted to have 142 amino acid residues of M-r 15,717 and shows
no significant similarity with known proteins. The predicted protein has three
possible consensus sequences for asparagine-linked glycosylation site. The CpPI
gene was expressed when mating-type minus (mt(-)) cells were incubated at a low
cell density in the light. Nitrogen deprivation from the medium enhances
expression of the CpPI gene. An analysis by genomic Southern hybridization
revealed that the cDNA probe hybridized to several DNA fragments obtained from
both the genome of mt(-) and mt(+) cells. However, in mt- cells, transcripts
for the PR-IF inducer could not be detected by Northern hybridization.
Schirmer A, Kolter R
Computational
analysis of bacterial sulfatases and their modifying enzymes
CHEM BIOL 5 (8): R181-R186 AUG 1998
Abstract:
The sequence analysis of enzymes that might modify bacterial sulfatases should
be useful in the task of identifying the human sulfatase-modifying homologs enzymes
that are defective in the rare inherited disease multi sulfatase deficiency.
Gladyshev MI, Sushchik NN, Kalachova GS, et al.
The effect of
algal blooms on the disappearance of phenol in a small forest pond
WATER RES 32 (9): 2769-2775 SEP 1998
Abstract:
Using experimental microecosystems the kinetics of phenol disappearance in
small forest pond waters (
von Figura K, Schmidt B, Selmer T, et al.
A novel
protein modification generating an aldehyde group in sulfatases: its role in
catalysis and disease
BIOESSAYS 20 (6): 505-510 JUN 1998
Abstract:
In multiple sulfatase deficiency, a rare human lysosomal storage disorder, all
known sulfatases are synthesized as catalytically poorly active polypeptides.
Analysis of the latter has shown that they lack a protein modification that was
detected in all members of the sulfatase family. This novel protein
modification generates a 2-amino-3-oxopropanoic acid (C alpha-formylglycine)
residue by oxidation of the thiol group of a cysteine that is conserved among
all eukaryotic sulfatases, The oxidation occurs in the endoplasmic reticulum at
a stage when the nascent polypeptide is not yet folded. The aldehyde is part of
the catalytic site and is likely to act as an aldehyde hydrate. One of the
geminal hydroxyl groups accepts the sulfate during sulfate ester cleavage
leading to the formation of a covalently sulfated enzyme intermediate. The
other hydroxyl is required for the subsequent elimination of the sulfate and
regeneration of the aldehyde group. In some prokaryotic members of the
sulfatase gene family, the DNA sequence predicts a serine residue, and not a
cysteine, Analysis of one of these prokaryotic sulfatases, however, revealed
the presence of the C alpha-formylglycine indicating that the aldehyde group is
essential for all members of the sulfatase family and that it can be generated
from either cysteine or serine, (C) 1998 John Wiley & Sons, Inc.
Arai S, Takahashi H, Takano H, et al.
Isolation,
characterization, and chromosome mapping of an actin gene from the primitive
green alga, Nannochloris bacillaris (Chorophyceae)
J PHYCOL 34 (3): 477-485 JUN 1998
Abstract:
Historically, the genus Nannochloris has been classified using the morphology
of cell division, although the mechanics of division remain relatively poorly
understood. Nannochloris bacillaris reproduces by binary fission. Microscopic
observation with fluorescein isothiocyanate-phaloloidin showed that actin
filaments localized near the nucleus and appeared as a ring- or beltlike
structure in the septum-forming area in the middle of the cell during cell
division. In primitive unicellular Chlorophyta such as N. bacillaris, actin is
also thought to play important roles in nuclear migration and cell division.
The N. bacillaris actin gene has three exons and two introns defined by two
exon-intron junctions with splice site consensus sequences. The two introns are
located at codons specifying amino acids 3/4 and 47/48. One of these, intron
position 3/4, is conserved in the actin gene of Saccharomyces cerevisiae. The
actin gene product was predicted to be 378 amino acids long with an estimated
molecular weight of 42 kDa. There is only one copy of the actin gene in the N.
bacillaris genome. Nannochloris bacillaris has 14 chromosomes that range in
size from 230 kb to 3000 kb, and the total size of the genome was estimated to be
20.3 Mb. The actin gene is on either chromosome XI or XII. In a phylogenetic
tree based on the actin gene sequence, N. bacillaris diverged before the
divergence of Volvox, Chlamydomonas, and higher plants, and very shortly
after the radiation of the Rhodophyta.
Amon P, Haas E, Sumper M
The
sex-inducing pheromone and wounding trigger the same set of genes in the
multicellular green alga Volvox
PLANT CELL 10 (5): 781-789 MAY 1998
Abstract:
The sex-inducing pheromone of the multicellular green alga Volvox
carteri is a glycoprotein that triggers development of males and females at a
concentration <10(-16) M. By differential screening of a cDNA library, two
novel genes were identified that are transcribed under the control of this
pheromone. Unexpectedly, one gene product was characterized as a
lysozyme/chitinase, and the other gene product was shown to encode a
polypeptide with a striking modular composition. This polypeptide has a
cysteine protease domain separated by an extensin-like module from three
repeats of a chitin binding domain. In higher plants, similar protein families
are known to play an important role in defense against fungi. Indeed, we found that
the same set of genes triggered by the sexual pheromone was also inducible in
V. carteri by wounding.
Hallmann A, Godl K, Wenzl S, et al.
The highly
efficient sex-inducing pheromone system of Volvox
TRENDS MICROBIOL 6 (5): 185-189 MAY 1998
Abstract:
The green alga Volvox is one of the simplest multicellular organisms and
is capable of both asexual and sexual reproduction. Sexual development is
initiated by a glycoprotein pheromone that acts at a concentration below
10(-16) M. The extracellular matrix (ECM) appears to play a key role in signal
amplification: several ECM proteins contain a domain with homology to the
sex-inducing pheromone.
El-Naggar MEE, Shaaban-Dessouki SA, Abdel-Hamid MI, et al.
Studies on
the phytoplankton populations and physico-chemical conditions of treated sewage
discharged into Lake Manzala in Egypt
MICROBIOLOGICA 21 (2): 183-196 APR 1998
Abstract:
Over a full year, the phytoplankton populations and physico-chemical conditions
of treated sewage discharged into
A remarkable seasonal variation in species
composition and standing crop of the phytoplankton populations was noted during
the study. The total phytoplankton standing crop appeared to be mainly
dependent on the growth of certain species viz., Oscillatoria chalybea, O.
princepes, O. tenuis, Microcystis aeruginosa, Anabaena constricta (Cyanophyta),
Nitzschia obtusa, Bacillaria paradoxa, Cocconeis placentula, Cyclotella
meneghiniana (Bacillariophyta), Pandorina morum, Volvox sp.
(Chlorophyta) and Phacus curvicauda (Euglenophyta). The continuous presence of
Anabaena constricta and Nitzschia palea was recorded in the treated sewage. The
least represented algal divisions were Pyrrhophyta and Cryptophyta, both in
terms of quality and quantity.The data indicate that the secondary effluents
were unstable in their chemical features and grossly polluted. Therefore, the
treatment systems must treat the discharged sewage to a tertiary level before
discharging into
Corrette-Bennett J, Rosenberg M, Przybylska M, et al.
Positional
cloning without a genome map: Using 'Targeted RFLP Subtraction' to isolate
dense markers tightly linked to the regA locus of Volvox carteri
NUCLEIC ACIDS RES 26 (7): 1812-1818 APR 1 1998
Abstract:
The ability to isolate genes defined by mutant phenotypes has fueled the rapid
progress in understanding basic biological mechanisms and the causes of
inherited diseases. Positional cloning, a commonly used method for isolating
genes corresponding to mutations, is most efficiently applied to the small
number of model organisms for which high resolution genetic maps exist. We
demonstrate a new and generally applicable positional cloning method that
obviates the need for a genetic map. The technique is based on Restriction
Fragment Length Polymorphism (RFLP) Subtraction, a method that isolates RFLP
markers spanning an entire genome, The new method, Targeted RFLP Subtraction
(TRS), isolates markers from a specific region by combining RFLP Subtraction
with a phenotypic pooling strategy. We used TRS to directly isolate dense
markers tightly linked to the regA gene of the eukaryotic green alga Volvox,
As a generally applicable method for saturating a small targeted region with
DNA markers, TRS should facilitate gene isolation from diverse organisms and
accelerate the process of physically mapping specific regions in preparation
for sequence analysis.
ten Lohuis MR, Miller DJ
Genetic
transformation of dinoflagellates (Amphidinium and Symbiodinium): expression of
GUS in microalgae using heterologous promoterconstructs
PLANT J 13 (3): 427-435 FEB 1998
Abstract:
Genetic transformation of two dinoflagellates (Amphidinium sp., Symbiodinium
microadriaticum) was achieved using plasmid constructs containing the neomycin
phosphotransferase gene (nptll) fused to the Agrobacterium nos promoter, or the
hygromycin B phosphotransferase gene (hpt) fused to the bidirectional
Agrobacterium p1'2' promoter. Gene transfer into intact (walled) dinoflagellate
cells was achieved by agitation in the presence of silicon carbide (SiCa)
whiskers. Transformation rates of 5-24 transformants per 10(7) cells were
obtained. Southern hybridization of transformants revealed stable integration
of multiple copies of the constructs. Activity of integrated copies of the
beta-glucoronidase (GUS) reporter gene coupled to the cauliflower mosaic virus
35S promotor or the p1'2' promoter was confirmed both histochemically and
fluorometrically. This is the first report of successful application bf
heterologous and widely used promoter and reporter genes in microalgae, and is the
first demonstration of transformation of a dinoflagellate. There appear to be
no substantial barriers to transformation of Amphidinium and Symbiodinium,
which must now be considered as the first of the dinoflagellate genera
accessible to genetic manipulation.
Miller SM, Kirk DL
glsA, a Volvox gene required for asymmetric
division and germ cell specification encodes a chaperone-like protein
MOL BIOL CELL 9: 1694 Suppl. S NOV 1998
Bell G
Volvox - Molecular-genetic origins of multicellularity and
cellular differentiation
SCIENCE 282 (5387): 248-248
Sumper M, Hallmann A
Biochemistry
of the extracellular matrix of Volvox
INT REV CYTOL 180: 51-85 1998
1997
Kirk DL
The genetic
program for germ-soma differentiation in Volvox
ANNU REV GENET 31: 359-380 1997
Abstract:
Volvox carteri possesses only two cell types: mortal somatic cells and
potentially immortal asexual reproductive cells called gonidia. Mutational
analysis indicates that three categories of genes play central roles in
programming this germ-soma division of labor: First the gls genes function
during embryogenesis to cause asymmetric divisions that produce large and small
cells. Then the lag genes act in the large cells (gonidial initials) to repress
functions required for somatic development while the regA locus acts in the
small cells (somatic initials) to repress functions required for reproductive
development. Transposon tagging and DNA transformation have recently been used
to recover and characterize the glsA and regA genes, and the sequences of these
genes lead to testable hypotheses about how they play their roles in germ-soma
differentiation.
Kroger N, Lehmann G, Rachel R, et al.
Characterization
of a 200-kDa diatom protein that is specifically associated with a silica-based
substructure of the cell wall
EUR J BIOCHEM 250 (1): 99-105
Abstract:
The cell wall of a diatom is made up of a silica-based scaffold and organic
macromolecules. Proteins located in the cell wall are believed to control
morphogenesis of the species-specific silica structures of the scaffold.
However, data that correlate distinct silica elements and specific proteins
within the diatom cell wall have not been reported. Here, the cell wall protein
HEP2OO (200-kDa HE-extractable protein) from the diatom Cylindrotheca
fusiformis is identified and characterized. HEP200 is tightly associated with a
substructure of the silica scaffold. It is a member of a new protein family, of
which two more members are identified. Each member displays the same bipartite
structure. The N-terminal part consists of a variable number of a repeated
sequence motif (PSCD domain), whereas the C-terminal part is unique,
Immunolocalization experiments revealed the arrangement of different proteins
within the cell wall. Frustulins, a previously described group of
glycoproteins, constitute the outer coat of the cell wall and exhibit a
ubiquitous distribution. In contrast, HEP200 is specifically located at a
subset of about six silica strips in intact cell walls, shielded by frustulins.
This study therefore identifies a diatom cell wall protein (HEP200) that is
associated with a distinct substructure of the silica scaffold.
Kurvari V
Cell wall
biogenesis in Chlamydomonas: molecular characterization of a novel protein
whose expression is up-regulated during matrix formation
MOL GEN GENET 256 (5): 572-580 NOV 1997
Abstract:
In the unicellular eukaryote Chlamydomonas, disruption of cell-matrix
interactions by treatment with a periplasmic matrix metalloproteinase, g-lysin,
activates a signal transduction pathway that results in the rapid synthesis and
secretion of matrix molecules, followed by their assembly into a new matrix. I
have identified and partially characterized several cDNA clones for transcripts
that are dramatically up-regulated following treatment of cells with g-lysin.
Here I report the complete nucleotide sequence and preliminary characterization
of a matrix-related molecule termed Mrp47. The cDNA clone for Mrp47 contained
an insert of 2.5 kb, corresponding to a transcript of 3.0 kb that is encoded by
a single-copy gene. Sequence analysis indicated that Mrp47 cDNA contains an
open reading frame (ORF) that encodes a 46-kDa polypeptide. The putative
polypeptide is unusually rich in the amino acids proline, alanine and serine,
with prolines clustered together in a 30-amino acid N-terminal region and a
80-amino acid C-terminal region. Further analysis of the predicted amino acid
sequence suggested that Mrp47 is likely to be a secreted glycoprotein. Southern
hybridization analysis indicated that Mrp47 is encoded by a single-copy gene in
the Chlamydomonas genome. Database searches suggested that Mrp47 shows homology
to other proline-rich proteins including a surface glycoprotein in Volvox
and verprolin from yeast.
Hoops HJ
Motility in
the colonial and multicellular Volvocales: structure, function, and evolution
PROTOPLASMA 199 (3-4): 99-112 1997
Abstract:
The colonial Volvocales are often said to be composed of Chlamydomonas-like
cells, but there are substantial differences in motility and flagellar
apparatus construction between the unicellular forms and the individual members
of a colony or spheroid. These changes appear to be required for effective
organismal motion and might possibly limit the rate at which new colonial forms
evolve from unicellular ones. The flagellar-beat envelopes in colonial members
are modified such that they beat in the same direction and in parallel planes
with their effective strokes at right angles to the cellular anterior-posterior
axis. These changes result from a series of developmental events of the
flagellar apparatus of the colonial forms while the colony is still an embryo.
Differences in the flagellar-apparatus structure in the members of the
Goniaceae and Volvocaceae are not obviously correlated with the traditional
placement of these algae in a simple volvocine lineage. Effective colonial
motion clearly requires precise positioning and rotational orientation of the
cells within the colony. Almost any arrangement where the cells are placed with
rotational symmetry within the colony results in colonial progression with
rotation. Such rotational symmetry is present from the time of embryogenesis.
The mechanism that leads to organismal steering in behavioral responses (e.g.,
phototaxis) must likewise differ between colonial and unicellular forms. Ln at
least some cases, this appears to result from changes in beat frequency in some
parts of the spheroid, but changes in beat direction cannot be ruled out for
all forms.
Hegemann P
Vision in
microalgae
PLANTA 203 (3): 265-274 NOV 1997
Abstract:
Flagellate green algae such as Chlamydomonas and related genera are guided by
their eyes to places where light conditions are optimal for photosynthetic
growth. These eyes constitute the simplest and most common visual system found
in nature. The eyes contain optics, photoreceptors and the elementary
components of a signal-transduction chain. Rhodopsin serves as the
photoreceptor, as it does in animal vision. Upon light stimulation, its
all-trans-retinal chromophore isomerizes into 13-cis and activates a
photoreceptor channel which leads to a rapid Ca2+ influx into the eyespot
region. At low light levels, the depolarization activates small flagellar
currents which induce in both flagella small but slightly different beating
changes resulting in distinct directional changes. In continuous light, Ca2+
fluxes serve as the molecular basis for phototaxis. In response to flashes of
higher energy the larger photoreceptor currents trigger a massive Ca2+ influx
into the flagella which causes the well-known phobic response. The
identification of proteins contributing to this signalling system has just
begun with the isolation and cloning of the opsins from Chlamydomonas and Volvox.
These plant opsins are highly charged, are not typical seven-helix receptors,
and are believed to form a protein complex with the photoreceptor channel. In
Spermatozopsis, a G-protein has been found which interacts either directly with
the rhodopsin or with the rhodopsin-ion channel complex. By using insertional
mutagenesis, genes coding for proteins that are involved in signalling have
been tagged. One of them is connected to the flagellar channel and crucial for
the flagellar action potential. Elucidation of photoreception in flagellated
algae will provide deeper insight into the development of visual systems,
starting from single-celled organisms and moving up through higher animals.
Nozaki H, Ito M, Uchida H, et al.
Phylogenetic
analysis of Eudorina species (Valvocaceae, Chlorophyta) based on rbcL gene
sequences
J PHYCOL 33 (5): 859-863 OCT 1997
Abstract:
Species and varieties in the genus Eudorina Ehrenberg (Volvocaceae,
Chlorophyta) were evaluated on the basis of phylogenetic analyses of the large
subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (rbcL) gene sequence
from 14 strains of four Eudorina species, as well as from nine species of
Pleodorina and Volvox. The sequence data suggested that 10 of the 14
Eudorina strains form three separate and robust monophyletic groups within the
nonmonophyletic genus Eudorina. The first group comprises ail three strains
off. unicocca G. M. Smith; the second group consists of one of the E, elegans
Ehrenberg var elegans strains, the E. cylindrica Korshikov strain, and both E.
illinoisensis (Kofoid) Pascher strains; and the third group consists of two
monoecious varieties off, elegans [two strains of E. elegans var synoica
Goldstein and one strain of E. elegans var. carteri (G. hi. Smith) Goldstein].
In addition, E. illinoisensis represents a poly- or paraphyletic species within
the second group. The remaining four strains, all of which are assigned to E.
elegans var. elegans, are nonmonophyletic. Although their position in the
phylogenetic trees is more or less ambiguous, they are ancestral to other taxa
ill the large anisogamous/oogamous monophyletic group including Eudorina,
Pleodorina, and Volvox (except for sect. Volvox). Thus, the four
Eudorina groups resolved in the present molecular phylogeny do not correspond
with the species concepts of Eudorina based on vegetative morphology, but they
do reflect the results Of the previous intercrossing experiments and modes of
monoecious and dioecious sexual reproduction.
Dierks T, Schmidt B, VonFigura K
Conversion of
cysteine to formylglycine: A protein modification in the endoplasmic reticulum
P NATL ACAD SCI
Abstract:
In sulfatases a C-alpha-formylglycine residue is found at a position where
their cDNA sequences predict a cysteine residue. In multiple sulfatase
deficiency, an inherited lysosomal storage disorder, catalytically inactive
sulfatases are synthesized which retain the cysteine residue, indicating that
the C,-formylglycine residue is required for sulfatase activity. Using in vitro
translation in the absence or presence of transport competent microsomes we
found that newly synthesized sulfatase polypeptides carry a cysteine residue
and that the oxidation of its thiol group to an aldehyde is catalyzed in the
endoplasmic reticulum. A linear sequence of 16 residues surrounding the Cys-69
in arylsulfatase A is sufficient to direct the oxidation, This novel protein
modification occurs after or at a late stage of cotranslational protein
translocation into the endoplasmic reticulum when the polypeptide is not yet
folded to its native structure.
Hallmann A, Rappel A, Sumper M
Gene
replacement by homologous recombination in the multicellular green alga Volvox carteri
P NATL ACAD SCI
Abstract:
With only two different cell types, the haploid green alga Volvox
represents the simplest multicellular model system. To facilitate genetic investigations
in this organism, the occurrence of homologous recombination events was
investigated with the intent of developing methods for gene replacement and
gene disruption. First, homologous recombination between two plasmids was
demonstrated by using overlapping nonfunctional fragments of a recombinant
arylsulfatase gene (tubulin promoter/arylsulfatase gene). After bombardment of Volvox
reproductive cells with DNA-coated gold microprojectiles, transformants
expressing arylsulfatase constitutively were recovered, indicating the presence
of the machinery for homologous recombination in Volvox. Second, a well
characterized loss-of-function mutation in the nuclear nitrate reductase gene
(nitA) with a single G --> A nucleotide exchange in a 5'-splice site was
chosen as a target for gene replacement. Gene replacement by homologous
recombination was observed with a reasonably high frequency only if the
replacement vector containing parts of the functional nitrate reductase gene
contained only a few nucleotide exchanges. The ratio of homologous to random
integration events ranged between
Raven JA
Multiple
origins of plasmodesmata
EUR J PHYCOL 32 (2): 95-101 MAY 1997
Abstract:
Plasmodesmata in photosynthetic eukaryotes are found in all embryophytes, in
many members of the Chlorophyta, and in the Phaeophyceae. The Phaeophyceae and
the Chlorophyta clearly developed cell walls and multicellularity
independently, sc that (in the absence of lateral gene transfer) plasmodesmata
evolved independently in these groups. The minimum number of independent
origins of plasmodesmata in the Chlorophyta based on molecular phylogenies is
two (Chlorophyceae sensu late, Charophyceae sensu late). Other intercellular
connections in members of the Chlorophyta (Ctenocladus, Smithsoniella, Volvox)
are structurally very different from true plasmodesmata. Recently published
taxonomies of the Chlorophyta have five classes (Chlorophyceae,
Oedegoniophyceae, Trentepohliophyceae, Klebsormidiophyceae and Charophyceae
sensu stricto) with plasmodesmata out of a total of thirteen. However, it is by
no means clear that these classes all acquired plasmodesmata independently.
Nozaki H, Ito M, Sano R, et al.
Phylogenetic analysis of Yamagishiella and
Platydorina (Volvocaceae, Chlorophyta) based on rbcL gene sequences
J PHYCOL 33 (2):
272-278 APR 1997
Abstract:
Yamagishiella, based on Pandorina unicocca Rayburn et Starr is distinguished
from Eudorina by its isogamous sexual reproduction, whereas Platydorina
exhibits anisogamous sexual reproduction. In the present study, rue sequenced
the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (rbcL)
genes from five Japanese and North American strains of Y. unicocca (Rayburn et
Stair) Nozaki, true Platydorina caudata Kofoid strains, and two strains of
Eudorina unicocca G. M. Smith, as well as eight related colonial and
unicellular species. Phylogenetic trees were constructed based on these
sequence data and on previously published rbcL gene sequences from 23
volvocalean species in order to deduce phylogenetic relationships within the
colonial Volvocales, with particular regard to the phylogenetic positions and
status of the genera Yamagishiella and Platydorina. Two robust monophyletic
groups of the anisogamous/oogamous volvocacean species were resolved in the
maximum-parsimony tree as well as in the neighbor-joining distance tree. One of
the two groups comprises three species of Volvox section Volvox,
whereas the other is composed of other sections of Volvox as well as of
all the species of Eudorina and Pleodorina. Platydorina, however, was
positioned outside these two monophyletic groups. Therefore, derivation of the
Platydorina lineage may be earlier than that of such anisogamous/oogamous
groups, or origin of ''anisogamy with sperm, packets'' in Platydorina may De
independent of sperm packet evolution in Eudorina, Pleodorina, and Volvox.
It was also resolved with high bootstrap values that all of the Y. unicocca
strains form a monophyletic group positioned outside the large monophyletic
group including Eudorina and Pleodorina. These reject the possibility of the
reverse evolution of isogamy from anisogamy to give rise to Yamagishiella
within the lineage of Eudorina.
Liss M, Kirk DL, Beyser K, et al.
Intron
sequences provide a tool for high-resolution phylogenetic analysis of volvocine
algae
CURR GENET 31 (3): 214-227 MAR 1997
Abstract:
Three nuclear spliceosomal introns in conserved locations were amplified and
sequenced from 28 strains representing 14 species and 4 genera of volvocalean
green algae. Data derived from the three different introns yielded congruent
results in nearly all cases. In pairwise comparisons, a spectrum of
taxon-specific sequence differences ranging from complete identity to no significant
similarity was observed, with the most distantly related organisms lacking any
conserved elements apart from exon-intron boundaries and a pyrimidine-rich
stretch near the 3' splice site. A metric (SI50), providing a measure of the
degree of similarity of any pair of intron sequences, was defined and used to
calculate phylogenetic distances between organisms whose introns displayed
statistically significant similarities. The rate of sequences divergence in the
introns was great enough to provide useful information about relationships
among different geographical isolates of a single species, but in most cases
was too great to provide reliable guides to relationships above the species
level. A substitution rate of approximately 3 x 10(-8) per intron position per
year was estimated, which is about 150-fold higher than in nuclear genes
encoding rRNA and about 10-fold higher than the synonymous substitution rate in
protein-coding regions. Thus, these homologous introns not only provide useful
information about intraspecific phylogenetic relationships, but also illustrate
the concept that different parts of a gene may be subject to extremely
different intensities of selection. The intron data generated here (1) reliably
resolve for the first;time the relationships among the five most extensively
studied strains of Volvox, (2) reveal that two other Volvox
species may be more closely related than had previously been suspected, (3)
confirm prior evidence that particular isolates of Eudorina elegans and
Pleodorina illinoisensis appear to be sibling taxa, and (4) contribute to the
resolution of several hitherto unsettled issues in Chlamydomonas taxonomy.
Godl K, Hallmann A, Wenzl S, et al.
Differential
targeting of closely related ECM glycoproteins: The pherophorin family from Volvox
EMBO J 16 (1): 25-34
Abstract:
The alga Volvox carteri represents one of the simplest multicellular organisms.
Its extracellular matrix (ECM) is modified under developmental control, e.g.
under the influence of the sex-inducing pheromone that triggers development of
males and females at a concentration below 10(-16) M. A novel ECM glycoprotein
(pherophorin-S) synthesized in response to this pheromone was identified and
characterized. Although being a typical member of the pherophorins, which are
identified by a C-terminal domain with sequence homology to the sex-inducing
pheromone, pherophorin-S exhibits a completely novel set of properties. In
contrast to the other members of the family, which are found as part of the
insoluble ECM structures of the cellular zone, pherophorin-S is targeted to the
cell-free interior of the spherical organism and remains in a soluble state. A
main structural difference is the presence of a polyhydroxyproline spacer in
pherophorin-S that is linked to a saccharide containing a phosphodiester bridge
between two arabinose residues. Sequence comparisons indicate that the self-assembling
proteins that create the main parts of the complex Volvox ECM have
evolved from a common ancestral gene.
1996
Stratmann J, Paputsoglu G, Oertel W
Differentiation
of Ulva mutabilis (Chlorophyta) gametangia and gamete release are controlled by
extracellular inhibitors
J PHYCOL 32 (6): 1009-1021 DEC 1996
Abstract:
Blade cells of Ulva mutabilis Foyn (Chlorophyta) excrete regulatory factors
into their cell walls and into the environment. These factors are essential for
the maintenance of the vegetative state. ''Sporulation inhibitor-1a'' (SI-1a)
is a glycoprotein that was isolated from the culture medium of axenic Ulva
growing as an undifferentiated callus. This protein was unusually stable to
denaturing treatments and showed an extremely high apparent molecular mass
(M(r)) of 1-4 X 10(7) daltons estimated by size exclusion chromatography. The
glycosylation was not essential for activity. SI-1a suppressed gametogenesis
completely at concentrations lower than 10(-14) M. When Ulva developed normally
in the presence of their symbiotic bacteria, smaller forms of SI-1 accumulated
in the medium (10(4) - 10(6) daltons). Sporulation inhibitors of the same size spectrum
and with similar properties were also extracted from crude cell walls of
nonaxenic Ulva. A class of different nonprotein sporulation inhibitors (SI-2)
of very low M(r) and yet unknown structure was isolated from the inner space
between the two blade cell layers. Excretion of all SI-1 forms decreased with
maturation of the thallus, whereas the overally concentration of SI-2 in the
thallus stayed constant throughout the life cycle. The SI-2 affected different
Ulva species whereas SI-1 was species-specific. Gametogenesis was induced upon
removal of both sporulation inhibitors from small single-layered fragments of
mature blades. After a ''determination phase'' of 23-46 h, dependent on the
time of induction within the cell cycle, the cells became irreversibly
committed to differentiation and were no longer susceptible to SI-1 or SI-2.
Subsequently, during a 28-h ''differentiation phase,'' 16 progametes were
formed by synchronous genome doublings and cell divisions and differentiated
into mature gametes. These became motile and were released from the gametangia
when the concentration of a ''swarming inhibitor'' of low M(r), excreted mainly
during the ''determination phase,'' declined below a threshold concentration.
The biochemical properties of these regulatory factors and their effects on
gametogenesis and gamete release are described.
Ichimura T
Genome
rearrangement and speciation in freshwater algae
HYDROBIOLOGIA 336 (1-3): 1-17
Abstract:
Speciation problems are reviewed in the context of biogeography of fresh-water
algae. Currently accepted species concept in phycology is based on
morphological characters, and according to this concept, most freshwater algal
species are considered cosmopolitan. This implies whether they have a highly
efficient means of dispersal or their morphological characters are very static
through a long evolutionary time. Recent studies of reproductive isolation show
that some biological species of fresh-water algae are not so static or may not
have such a high power of dispersal means, though some are indeed very static
in morphological characters. The life cycle of most freshwater algae is
composed of a vegetative cycle of growth and reproduction and a sexual cycle of
gametic fusion and meiosis in the zygote, which forms a dormant spore-like
structure. Since any freshwater habitat is ephemeral in terms of evolutionary
time scale, each species has a capacity of forming germlings from a dormant
cell in order to recycle its life history. The genome of freshwater algae,
therefore, contains various coadapted gene systems, at least two, for the
vegetative and for the sexual cycle. Homothallism and heterothallism are two
contrasting mating systems that represent two opposing ways of life to
harmonize antagonism between the vegetative stage of growth and reproduction
and the sexual and dormant stage. Geographic and ecological distribution,
polyploidy, and sex determination are discussed in conjunction with sexual and
postzygotic isolating mechanisms.
Nozaki H
Morphology
and evolution of sexual reproduction in the Volvocaceae (Chlorophyta)
J PLANT RES 109 (1095): 353-361 SEP 1996
Abstract:
Morphological features of sexual reproduction in the Volvocaceae are reviewed,
focusing particularly on gametic union and zygote germination. Both of the two
conjugating gametes of the isogamous genera Pandorina, Volvulina and
Yamagishiella bear a tubular mating structure (mating papilla), and plasmogamy
is initiated by union of the papillae tips. On zygote germination, a single
biflagellate gone cell is released from the zygote wall. Although all the
anisogamous and oogamous genera of the Volvocaceae produce ''sperm packets''
during gametogenesis and a single gone cell at zygote germination, some
difference can be recognized in the male gametes. The male gametes of Eudorina
bear a tubular cytoplasmic protuberance (putative mating papilla) near the base
of the flagella, whereas such a structure recognized at the light microscopic
level is not evident in Pleodorina and Volvox, Evolution of the sexual
reproduction characteristics of volvocacean algae is discussed on the basis of
recent cladistic analysis of morphological data as well as of the ribosomal (r)
RNA phylogeny and large subunit of the ribulose-1,5-biphosphate
carboxylase/oxygenase(rbcL) gene trees.
Beyser K, Fabry S
Identification
and characterization of a lower plant Ypt/Rab guanosine dissociation inhibitor
(GDI)
FEBS LETT 396 (2-3): 298-304
Abstract:
The cDNA encoding a Ypt/Rab guanosine dissociation inhibitor (Ypt-GDI) was
isolated from the multicellular green alga Volvox carteri, representing
the first complete plant gdi gene described. The gdiV1 gene occurs as a single
copy in the algal genome, indicating that its product regulates all YptV
proteins from Volvox. The derived GDI protein (GDIV1p) shows high
similarity to animal and fungal GDIs. A specific antibody developed against
GDIV1p detected the protein throughout the whole Volvox life-cycle. GDIV1p
was localized in the cytoplasm and in the algal flagellum. This is in line with
earlier findings of a dual localization of Ypt proteins both in the cell body
and in the motility organelle, and indicates a novel role of the GDI/Ypt
system, possibly in intraflagellar transport.
Choi G, Przybylska M, Straus D
Three
abundant germ line-specific transcripts in Volvox carteri encode photosynthetic proteins
CURR GENET 30 (4): 347-355 SEP 1996
Abstract:
Volvox carteri is a multicellular eukaryotic green alga composed of
about 2000 cells of only two differentiated types: somatic and germ line. To
understand how embryonic cells are assigned either to somatic or germ line
fates, we are investigating the regulation of transcripts that are abundant in
only one cell type. Here we report the identity of three
transcripts that are coordinately expressed at high levels in germ line cells but not in somatic cells. Surprisingly, all three transcripts encode photosynthetic chloroplast proteins (light-harvesting complex protein. oxygen-evolving enhancer protein 3, and ferredoxin-NADP(+) reductase) that are transcribed from nuclear genes. We discuss why these mRNAs might be required at high levels in germ line cells and present a hypothesis, suggested by our results, on the evolution of cell specialization in the Volvocales.
Ortega MA, DiazGuerra M, Sastre L
Actin gene
structure in two Artemia species, A-franciscana and A-parthenogenetica
J MOL EVOL 43 (3): 224-235 SEP 1996
Abstract:
Genomic clones coding for actin have been isolated from two species of the
crustacean Artemia, A. parthenogenetica and A. franciscana. The Act211 isoform
gene was isolated from A. parthenogenetica, and the two other isoform genes,
Act302 and Act403, were isolated from A. franciscana. The comparison of the
nucleotide sequence of genomic and cDNA clones showed an interspecific
divergence of 4% in translated and 6.1% in untranslated regions. However, the
establishment of the partial structure of the Act211 gene in A. franciscana and
of the Act302 gene in A. parthenogenetica suggests their similarity in the two
species. The Act211 gene is divided into four exons, the Act302 gene into six
exons, and the Act403 gene into seven exons. The three genes have introns in
the 5' untranslated region and between codons 41 and 42. The Act211 and 403
genes have one common intron in codon 168. The Act302 and 403 genes have common
introns between codons 121-122, 246-247, and within codon 301. While introns in
the 5' untranslated region and between codons 41-42 and 121-122 are present in
many organisms, the introns in positions 168 and 246-247 had only been found
previously in actin genes from the nematode Onchocerca volvulus and the green
alga Volvox carterii, respectively. The intron in position 301 had not
been reported before. The transcription initiation sites of these three genes
as well as the nucleotide sequences of the promoter regions have been also
determined.
Huber H, Beyser K, Fabry S
Small G
proteins of two green algae are localized to exocytic compartments and to
flagella
PLANT MOL BIOL 31 (2): 279-293 MAY 1996
Abstract:
The Ypt/Rab proteins are small GTPases, which belong to the Ras superfamily and
have been shown to be involved in endo- and exocytosis in mammalian cells and
yeast. Using affinity-purified antibodies specific for four Ypt proteins,
namely Ypt1p, Ypt4p, Ypt5p and Ypt6p, of the multicellular green alga Volvox
carteri (YptVp) and its close unicellular relative Chlamydomonas reinhardtii (YptCp),
we examined the abundance of the corresponding antigens during the asexual life
cycle of Volvox, and their intracellular localization. The YptV proteins
were found in all stages throughout the asexual life cycle and are tightly
associated with intracellular membranes. Indirect immunofluorescence revealed
that YptV4p, YptV5p and YptV6p are present in perinuclear regions of the cell,
indicating an association with the Golgi region. Golgi localization of YptV4p
and YptV6p in Volvox was confirmed by immunogold electron microscopy. In
contrast, we found Ypt1p associated with the contractile vacuole in both V.
carteri and C. reinhardtii. Furthermore, the YptV proteins were also detected
along the entire length of the flagella of somatic Volvox cells. This
flagellar location was substantiated by western blot analysis of extracts
prepared from isolated flagella of both algae. While localization to exocytic
compartments is in agreement with the established Ypt/Rab function in
intracellular vesicle transport of eukaryotic cells, presence in the algal
flagellum is the first hint of a possible role for small G proteins also in
motility organelles.
Ferris PJ, Woessner JP, Goodenough UW
A sex
recognition glycoprotein is encoded by the plus mating-type gene fus1 of
Chlamydomonas reinhardtii
MOL BIOL CELL 7 (8): 1235-1248 AUG 1996
Abstract:
Sexual fusion between plus and minus gametes of the unicellular green alga Chlamydomonas
reinhardtii entails adhesion between plus-specific and minus-specific
''fringe'' proteins displayed on the plasma membrane of gametic mating
structures. We report the identification of the gene (fus1) encoding the plus
fringe glycoprotein, which resides in a unique domain of the mating-type plus
(mt(+)) locus, and which was identified by transposon insertions in three
fusion-defective mutant strains. Transformation with fus1(+) restores fringe
and fusion competence to these mutants and to the pseudo-plus mutant imp11
mt(-), defective in minus differentiation. The fus1 gene is remarkable in
lacking the codon bias found in all other nuclear genes of C. reinhardtii.
Gruber H, Kirzinger SH, Schmitt R
Expression of
the Volvox gene encoding nitrate
reductase: Mutation-dependent activation of cryptic splice sites and
intron-enhanced gene expression from a cDNA
PLANT MOL BIOL 31 (1): 1-12 APR 1996
Abstract:
Use of the nitrate reductase encoding gene (nitA) as selection marker has
facilitated the successful nuclear transformation of Volvox carteri. The
Volvox nitA gene contains 10 introns. A stable nitA mutation in the Volvox
recipient strain 153-81 resides in a G-to-A transition of the first nucleotide
in the 5' splice site of nitA intron 2. This mutation resulted in at least
three non-functional splice variants, namely: (1) intron 2 was not spliced at
all; (2) a cryptic 5' splice site 60 nt upstream or (3) a cryptic 5' splice
site 16 nt downstream of the mutation were activated and used for splicing.
When we used nitA cDNA (pVcNR13) for transformation of V. carteri 153-81, a low
efficiency of about 5 x 10(-5) transformants per reproductive cell was observed.
Re-integration of either intron 1 (pVcNR15) or introns 9 and 10 (pVcNR16) in
the transforming cDNA increased transformation rates to 5 x 10(-4). In
parallel, pVcNR15-transformed Volvox exhibited growth rates that were
100-fold increased over the pVcNR13-transformed alga. This intron-enhancement
of nitA gene expression appears to be associated with post-transcriptional
processing and 'channelling' of the message. These data suggest an important
role of splicing for gene expression in V. carteri.
Agrawal SC, Sharma
Chemical and
biological properties of culture filtrates of Westiellopsis prolifica and
Chaetophora attenuata
ISRAEL J PLANT SCI 44 (1): 43-48 1996
Abstract:
Westiellopsis prolifica Janet and Chaetophora attenunta Hazen cultures released
sugars (glucose, fructose, and sucrose), organic acids (oxaloacetic acid and
oxalic acid), amino acids, and protein. W. prolifica cultures released the amino
acids glycine, serine, cystine, glutamic acid, aspartic acid, and cc-alanine,
while C. attenuata cultures released glycine, serine, aspartic acid, and
cr-alanine. W. prolifica and C. attenuata cultures of all ages released more
extracellular protein than total free amino acids. Cultures of C. attenuata
released more protein than cultures of the same age of W. prolifica. The
filtrates from old cultures of W. prolifica and C. attenunta decreased the
total chlorophyll content of all algae tested, totally suppressed conjugation
in Spirogyra decimina and zoospore formation in C. attenuata, and drastically
decreased spore germination in W. prolifica, thus producing stressful
conditions affecting the growth and reproduction of these and other algae.
Selmer T, Hallmann A, Schmidt B, et al.
The
evolutionary conservation of a novel protein modification, the conversion of
cysteine to serinesemialdehyde in arylsulfatase from Volvox carteri
EUR J BIOCHEM 238 (2): 341-345
Abstract:
A novel post-translational protein modification has recently been described in
two human sulfatases, by which a cysteine is replaced by a serinesemialdehyde
(2-amino-3-oxopropionic acid) residue [Schmidt, B., Selmer, T., Ingendoh, A.
& von Figura, K. (1995) Cell 82, 271-278]. This cysteine is conserved among
all known eukaryotic sulfatases. Here we report the presence of this
modification in arylsulfatase from the green alga Volvox carteri. The
evolutionary conservation of this novel protein modification between sulfatases
of V. carteri and man lends further support to the assumption that this
modification is required for the catalytic activity of sulfatases and may be
present in all sulfatases of eukaryotic origin.
Sugase Y, Hirono M, Kindle KL, et al.
Cloning and
characterization of the actin-encoding gene of Chlamydomonas reinhardtii
GENE 168 (1): 117-121
Abstract:
The genomic and complementary DNA sequences were determined for the unique
actin-encoding gene in Chlamydomonas reinhardtii (Cr). The deduced amino acid
(aa) sequence of this actin was similar to most known actin sequences, with the
highest identity (98.1%) being with that of Volvox carteri actin. The Cr
actin-encoding gene has one intron in the 5'-untranslated region and eight
introns in the coding region. The latter eight introns occur at the same
positions as those in the V. casteri actin-encoding gene. The 5'-upstream
region contains four short stretches of sequence similar to the so-called 'tub
box', a characteristic sequence proposed to be responsible for the regulation
of synthesis of various axonemal proteins upon deflagellation and during the
cell cycle, Southern blot analysis indicated that the Cr genome has only a
single actin-encoding gene. An antibody specific for the 11-aa peptide
corresponding to the N-terminal sequence of this actin was found to react with
a 43-kDa protein associated with flagellar inner-arm dynein. These findings
indicate that a single actin functions in both the cytoplasm and flagella of
this organism.
Fabry S, Beyser K
YptV2p, a
membrane-associated small G protein abundant during embryogenesis in the green
alga Volvox carteri
PROTOPLASMA 190 (1-2): 79-87 1996
Abstract:
The multicellular fresh-water alga Volvox carteri contains at least six
small G protein-encoding genes (ypt genes) whose products are probably involved
in intracellular vesicle transport. Four of them, YptV1, YptV3, YptV4, and
YptV5, have been isolated and characterized previously. Here we report the
cloning of yptV2 cDNA, the production of recombinant His-tagged YptV2p protein
(reYptV2p) in E. coli, and the analysis of its GTPase activity and
intracellular localization. YptV2p is predominantly present in dividing Volvox
embryos. It is a membrane-associated protein which is localized to the cell
periphery (plasma membrane or plasma-membrane-associated vesicles), probably by
a lipid moiety. Purified, E. coli-expressed YptV2p binds GTP specifically, and
has a typically low intrinsic GTPase activity (k(cat) = 0.004/min), which is
enhanced by a GTPase activating protein activity present in Volvox. Our
observations suggest a role of YptV2p in secretion, with a peak during the
rapid cleavages of the Volvox embryo.
Hallmann A, Sumper M
The Chlorella
hexose H+ symporter is a useful selectable marker and biochemical reagent when
expressed in Volvox
P NATL ACAD SCI USA 93 (2): 669-673 JAN 23 1996
Abstract:
The multicellular obligately photoautotrophic alga Volvox is composed of
only two types of cells, somatic and reproductive, Therefore, Volvox
provides the simplest model system for the study of multicellularity. Metabolic
labeling experiments using radioactive precursors are crucial for the detection
of stage- and cell-type-specific proteins, glycoproteins, lipids, and
carbohydrates. However, wild-type Volvox lacks import systems for sugars
or amino acids. To circumvent this problem, the hexose/H+ symporter (HUP1) gene
from the unicellular alga Chlorella was placed under the control of the
constitutive Volvox beta-tubulin promoter. The corresponding transgenic Volvox
strain synthesized the sugar transporter in a functional state and was able to
efficiently incorporate C-14 from labeled glucose or glucosamine. Sensitivity
toward the toxic glucose/mannose analogue 2-deoxyglucose increased by orders of
magnitude in transformants. Thus we report the successful transformation of Volvox
with a gene of heterologous origin. The chimeric gene may be selected for in
either a positive or a negative manner, because transformants exhibit both
prolonged survival in the dark in the presence of glucose and greatly increased
sensitivity to the toxic sugar 2-deoxyglucose. The former trait may make the
gene useful as a dominant selectable marker for use in transformation studies,
whereas the latter trait may make it useful in development of a gene-targeting
system.
Nishii I, Ogihara S
Role of
actomyosin in multicellular deformation: Inversion of Volvox embryos.
MOL BIOL CELL 7: 2219-2219 Suppl. S DEC 1996
Girardin HM, Pelletier JA, Jovanovic L, et al.
Translational
control during the development of Volvox.
MOL BIOL CELL 7: 624-624 Suppl. S DEC 1996
1995
Nozaki H, Itoh M, Sano R, et al.
Phylogenetic
relationships within the colonial volvocales (Chlorophyta) inferred from rbcL
gene sequence data
J PHYCOL 31 (6): 970-979 DEC 1995
Abstract:
The chloroplast-encoded large subunit of the ribulose-1, 5-bisphosphate
carboxylase/oxygenase (rbcL) gene was sequenced from 20 species of the colonial
Volvocales (the Volvacaceae, Goniaceae, and Tetrabaenaceae) in order to
elucidate phylogenetic relationships within the colonial Volvocales. Eleven
hundred twenty-eight base pairs In the coding regions of the (rbcL) gene were
analyzed by the neighbor-joining (NJ) method using three kinds of distance
estimations, as well as by the maximum parsimony (MP) method. A large group
comprising all the anisogamous and oogamous volvocacean species was resolved in
the MP tree as well as in the NJ trees based on overall and synonymous
substitutions. In all the trees constructed, Basichlamys and Tetrabaena
(Tetrabaenaceae) constituted a very robust phylogenetic group. Although not
supported by high bootstrap values, the MP tree and the NJ tree based on
nonsynonymous substitutions indicated that the Tetrabaenaceae is the sister
group to the large group comprising the Volvocaceae and the Goniaceae. In
addition, the present analysis strongly suggested that Pandorina and
Astrephomene are monophyletic genera whereas Eudorina is nonmonophyletic. These
results are essentially consistent with the results of the recent cladistic
analyses of morphological data. However, the monophyly of the Volvocaceae
previously supported by four morphological synapomorphies is found only in the
NJ tree based on nonsynonymous substitutions (with very low bootstrap values).
The genus Volvox was clearly resolved as a polyphyletic group with V.
rousseletii Pocock separated from other species of volvox in the rbcL
gene comparisons, although this genus represents a monophyletic group in the
previous morphological analyses. Furthermore, none of the rbcL gene trees
supported the monophyly of the Goniaceae; Astrephomene was placed in various
phylogenetic positions.
Memon A, Hwang SB, Deshpande N, et al.
Novel aspects
of the regulation of a cDNA (Arf1) from Chlamydomonas with high sequence
identity to animal ADP-ribosylation factor 1
PLANT MOL BIOL 29 (3): 567-577 NOV 1995
Abstract:
ADP-ribosylation factor (ARF) is a highly conserved, low molecular mass (ca. 21
kDa) GTP-binding protein that has been implicated in vesicle trafficking and
signal transduction in yeast and mammalian cells. However, little is known of
ARF in plant systems. A putative ARF polypeptide was identifed in subcellular
fractions of the green alga Chlamydomonas reinhardtii, based on [P-32]GTP
binding and immunoblot assays. A cDNA clone was isolated from Chlamydomonas
(Arfl), which encodes a 20.7 kDa protein with 90% identity to human ARF1.
Northern blot analyses showed that levels of Arfl mRNA are highly regulated
during 12 h/12 h light/dark (LD) cycles. A biphasic pattern of expression was
observed: a transient
Imaizumi M, Doida Y
Cyclic AMP is
a signal for repression of differentiation into gametes in Micrasterias
thomasiana var notata
PLANT SCI 112 (1): 33-42
Abstract:
This study investigates the effects of adenosine 3':5'-cyclic monophosphate
(cAMP) and several chemicals which elevate the intracellular level of cAMP on
the induction of zygote formation in Micrasterias thomasiana var. notata. When
added at a concentration of 0.5-3 mM, cAMP repressed the induction of zygotes
and simultaneously promoted cell proliferation, although at a concentration of
0.1 mM it merely delayed the initiation of zygote induction. Methylxanthines
caffeine (0.05-1 mM) and theophylline (0.05-1 mM), forskolin (10 mu M), which
is a potent activator of adenylate cyclase, and a membrane-permeable cAMP
analog, 8-bromo cAMP (0.1-3 mM), also repressed the induction of zygotes and
simultaneously promoted cell proliferation. In contrast, another cAMP analog
used in this study, N-6,O-2'-dibutyryl cAMP (2-3 mM), repressed the induction
of zygotes but did not cause promotion of cell proliferation. This analog also
specifically blocked the cell division directly involved with gamete formation.
The results obtained suggest that intracellular cAMP may function as a signal
which simultaneously represses zygote induction and causes proliferation of
cells in Micrasterias.
DESNITSKI AG
On
the origin of Metazoa
ZH OBSHCH BIOL 56 (5): 629-631 SEP-OCT 1995
Abstract:
Under consideration is a new version of the phagocytella conception. It is suggested
to consider blastea not a particular organism but a morphologically variable
taxon of mixotrophic flagellates. Some of its subtaxa might have made a
transition to the true heterotrophy, thus having become direct metazoan
ancestors.
WALTHER Z, HALL JL
The uni chromosome of chalmydomonas – histone genes and nucleosome structure.
NUCLEIC ACIDS RES 23 (18): 3756-3763
Abstract:
The uni linkage group (ULG) of Chlamydomonas reinhardtii contains many genes
involved in the basal body-flagellar system, Recent evidence suggests that the
corresponding uni chromosome is located in close proximity to the basal body
complex. In the course of studies into its molecular organization, we have
found a cluster of four histone genes on the ULG. The genes are arranged as
divergently-transcribed pairs: H3-H4 and H2B-H2A. Genomic sequencing reveals
that these genes lack introns and contain characteristic 3' palindromes similar
to those of animals, The predicted amino acid sequences are highly conserved
across species, with greatest similarities to the histone genes of Volvox.
Southern analysis shows that each histone gene is present in 15-20 copies in
Chlamydomonas and suggests a dispersed genomic organization. Northern analysis
of mitotically-synchronized cells shows that, like the replication-dependent
histones of higher eukaryotes, Chlamydomonas histone genes are expressed during
S-phase. Using a gene-specific probe on Northern blots, we provide evidence
that the ULG H4 gene is regulated in the same manner as other Chlamydomonas
histone genes. Finally, micrococcal nuclease protection experiments show that
the uni chromosome itself associates with histone proteins and displays a
conventional nucleosomal banding pattern.
FABRY S, MULLER K, LINDAUER A, et al.
THE
ORGANIZATION STRUCTURE AND REGULATORY ELEMENTS OF CHLAMYDOMONAS HISTONE GENES
REVEAL FEATURES LINKING PLANT AND ANIMAL GENES
CURR GENET 28 (4): 333-345 SEP 1995
Abstract:
The genome of the green alga Chlamydomonas reinhardtii contains approximately
15 gene clusters of the nucleosomal (or core) histone H2A, H2B, H3 and H4 genes
and at least one histone H1 gene. Seven non-allelic histone gene loci were
isolated from a genomic library, physically mapped, and the nucleotide
sequences of three isotypes of each core histone gene species and one linked H1
gene determined. The core histone genes are organized in clusters of H2A-H2B
and H3-H4 pairs, in which each gene pair shows outwardly divergent
transcription from a short (< 300 bp) intercistronic region. These
intercistronic regions contain typically conserved promoter elements, namely a
TATA-box and the three motifs TGGCCAGG(G/C)-CGAG, CGTTGACC and CGGTTG.
Different from the genes of higher plants, but like those of animals and the
related alga Volvox, the 3' untranslated regions contain no poly A
signal, but a palindromic sequence (3' palindrome) essential for mRNA
processing is present. One single H1 gene was found in close linkage to a
H2A-H2B pair. The H1 upstream region contains the octameric promoter element
GGTTGACC (also found upstream of the core histone genes) and two specific
sequence motifs that are shared only with the Volvox H1 promoters. This
suggests differential transcription of the H1 and the core histone genes. The
H1 gene is interrupted by two introns. Unlike Volvox H3 genes, the three
sequenced H3 isoforms are intron-free. Primer-directed PCR of genomic DNA
demonstrated, however, that at least 8 of the about 15 H3 genes do contain one
intron at a conserved position. In synchronized C. reinhardtii cells, H4 mRNA
levels (representative of all core histone mRNAs) peak during cell division,
suggesting strict replication-dependent gene control. The derived peptide
sequences place C. reinhardtii core histones closer to plants than to animals,
except that the H2A histones are more animal-like. The peptide sequence of
histone H1 is closely related to the V. carteri VH1-II (66% identity).
Organization of the core histone gene in pairs, and non-polyadenylation of
mRNAs are features shared with animals, whereas peptide sequences and enhancer
elements are shared with higher plants, assigning the volvocalean histone genes
a position intermediate between animals and plants.
DESNITSKI AG
A
REVIEW ON THE EVOLUTION OF DEVELOPMENT IN VOLVOX - MORPHOLOGICAL AND PHYSIOLOGICAL-ASPECTS
EUR J PROTISTOL 31 (3): 241-247
Abstract:
This paper presents a morphophysiological concept of the evolution of Volvox
development. We use published data concerning differences in size of the mature
gonidia, rates of their division and peculiarities in segregation of somatic
and reproductive cell lines. Based on this, four programmes (types) of asexual
development of Volvox are recognized, and the evolutionary relationships
among these programmes (but not among any concrete species of Volvox)
are elucidated. The first developmental programme (Volvox powersii - V.
pocockiae) is clearly primitive for the genus. This programme is characterized
by ancestral features: large gonidia, division is fast, and there is no unequal
(asymmetric) division into two cellular types. The second developmental
programme(V. carteri), the third programme (V. tertius) and the fourth
programme (V. aureus) are all derived, but constitute different phylogenetic
trends. They each have some derived features: the second programme involves
asymmetric division, the third programm involves slow division, while the
fourth programme involves small gonidia and slow division. The evolutionary
concept is supplemented by data on sexual reproduction in various species of Volvox.
GODL K, HALLMANN A, RAPPEL A, et al.
PHEROPHORINS
- A FAMILY OF EXTRACELLULAR-MATRIX GLYCOPROTEINS FROM VOLVOX STRUCTURALLY RELATED TO THE SEX-INDUCING PHEROMONE
PLANTA 196 (4): 781-787 JUL 1995
Abstract:
Pherophorins are extracellular matrix (ECM) glycoproteins from Volvox
that share homology with the sex-inducing pheromone. A novel pherophorin (pherophorin
III) was characterized both with respect to expression pattern and proteolytic
processing in vivo. Furthermore, it was shown that the pherophorins represent a
protein family of ECM glycoproteins exhibiting a modular composition: their
N-terminally located domain is a homolog of a domain found in the ECM
glycoprotein SSG 185. Together with SSG 185, pherophorin I is a main component
of the cellular zone within the ECM. The Volvox genome contains a tandem
arrangement of genes encoding pherophorin II-related polypeptides. Inhibition
of proteolytic processing of pherophorin II and III in vivo appears to result
in the suppression of sexual induction.
DIETMAIER W, FABRY S, HUBER H, et al.
ANALYSIS OF A
FAMILY OF YPT GENES AND THEIR PRODUCTS FROM CHLAMYDOMONAS-REINHARDTII
GENE 158 (1): 41-50 MAY 26 19
Abstract:
Small G-proteins encoded by the ras-like ypt genes are ubiquitous in eukaryotic
cells. They have been shown to play an essential role in membrane vesicle
transport. We have isolated four ypt genes, yptC1, yptC4, yptC5 and yptC6, from
Chlamydomonas reinhardtii (Cr) genomic and cDNA libraries. Three of them,
yptC1, yptC4 and yptC5, are close homologues of ypt genes previously found in
the multicellular alga Volvox carteri (Vc), the fourth, yptC6, is new.
Each yptC gene is present as a single copy in the genome. Comparisons of genomic
and cDNA sequences revealed that the coding regions are interrupted by five
(yptC5), six (yptC6), seven (yptC4) and eight (yptC1) introns, respectively. Cr
ypt genes and the closely related Vc ypt genes have identical exon-intron
structures, but the corresponding intron sequences are completely different.
Polyadenylation is signalled by UAUAA, UGUAG and UGUAA. The deduced amino acid
(aa) sequence of YptC6 exhibited 79% identity with HRab2; YptC1, YptC4 and
YptC5 exhibited over 90% identity with their Vc homologues. Primary structures
of the 9-aa 'effector domain' and the contiguous 'helix3-loop7' motif (approx.
30 aa) are 'diagnostic' features for functional assignment. Recombinant YptC
proteins, overproduced in Escherichia coli and purified to near homogeneity,
displayed strong and specific binding of GTP, but not of GMP or ATP. The four
Cr Ypt proteins showed immunochemical cross reactions to their Vc counterparts.
Moreover, Western blots demonstrated at least six types of Ypt in both Cr and
Vc, suggesting that these Ypt are used for household functions responsible for
vesicle transport rather than for cellular differentiation.
VOIGT J, VOGELER HP, KONIG WA, et al.
CHAOTROPE-SOLUBLE
CELL-WALL GLYCOPROTEINS OF VOLVOX
AND SOME MEMBERS OF THE ZYGNEMATOPHYCEAE IMMUNOLOGICALLY RELATED TO THE 150 KDA
CELL-WALL GLYCOPROTEIN OF CHLAMYDOMONAS-REINHARDTII
MICROBIOL RES 150 (2): 129-137 MAY 1995
Abstract:
As previously described, the cell wall of Chlamydomonas reinhardtii contains
several chaotrope-soluble glycoproteins with similar sugar compositions, but
considerably different proportions of hydroxyproline. All these
hydroxyproline-containing cell wall glycoproteins are recognized by a
polyclonal antibody raised against the purified '150 kDa' cell wall
glycoprotein of Chlamydomonas reinhardtii. This antibody also cross-reacts with
some polypeptides present in the LiCl-extracts from intact cells of Spirotaenia
erythrocephala, Spirotaenia obscura, Volvox aureus, and Volvox
globator as revealed by Western blot analyses. Therefore, an Ige fraction of
this particular antibody coupled to CNBr-activated Sepharose was used to
isolate the immunologically related polypeptides extracted by aqueous LiCl from
intact cells or cell wall preparations of different green algae belonging to
the Volvocales or to the Zygnematophycene. Different and more or less complex
polypeptide patterns were observed by comparative SDS-PAGE analyses of the
polypeptide fractions isolated by immunoaffinity chromatography from extracts
of Chlamydamonas reinhardtii, Volvox aureus, Micrasterias rotata,
Gonatozygon brebissonii and Netrium digitus, respectively, whereas the
corresponding fraction prepared from Spirotaenia erythrocephala contained a
predominant '160 kDa' component. Amino acid and sugar analyses revealed that
all these polypeptide fractions contained hydroxyproline (1.0-4.5 mol%) and the
same sugars as the Chlamydomonas cell wall glycoproteins. However, the relative
amounts of these sugars (arabinose, galactose, glucose, mannose and xylose)
were found to be rather different. The highest proportion of hydroxyproline
(4.5 mol%) and the highest ratio of arabinose:galactose (4.75:1) were determined
for the glycoprotein fraction isolated from Spirotaenia erythrocephala
indicating that at least the predominant '160 kDa' component is an intrinsic
cell wall glycoprotein containing hydroxyproline and oligo-arabinosyl side
chains. All the polypeptide fractions isolated from the other green algae
obviously also contained chaotropesoluble cell wall glycoproteins as revealed
by the presence of arabinose and hydroxyproline. These findings show that all
the investigated green algae contain chaotrope-soluble cell wall glycoproteins
immunologically related to the '150 kDa' cell wall glycoprotein of
Chlamydomonas reinhardtii.
FABRY S, STEIGERWALD R, BERNKLAU C, et al.
STRUCTURE-FUNCTION
ANALYSIS OF SMALL G-PROTEINS FROM VOLVOX
AND CHLAMYDOMONAS BY COMPLEMENTATION OF SACCHAROMYCES-CEREVISIAE YPT/SEC
MUTATIONS
MOL GEN GENET 247 (3): 265-274
Abstract:
cDNAs representing nine small G protein genes encoding Ypt proteins from the
green algae Volvox carteri (YptV) and Chlamydomonas reinhardtii (YptC)
were tested for their ability to complement mutations in the YPT1, SEC4, and
YPT7 genes of Saccharomyces cerevisiae strains defective in different steps of
intracellular vesicle transport. None of the heterologously expressed algal
genes was able to complement mutations in SEC4 or YPT7, but three of them,
yptV1, yptC1, and yptV2, restored a YPT1 null mutation. On the amino acid
sequence level, and particularly with respect to known small G protein
specificity domains. YptV1p and YptC1p are the closest algal analogs of yeast
Ypt1p, with 70% overall identity and identical effector regions, but YptV2p is
only 55% identical to Ypt1p, and its effector domain resembles that of Sec4p.
To define more precisely the regions that supply Ypt1p function, six chimeras
were constructed by reciprocal exchange of 68/72-, 122/123-, and 162/163-amino
acid segments of the C-terminal regions between YptV1p (complementing) and YptV3p
(non-complementing). Segments containing 68 amino acids of the hypervariable
C-terminal, and 41 residues of the N-terminal region including the effector
region, of YptV1p could be replaced by the corresponding parts of YptV3p
without loss of function in yeast, but exchanges within the central core
destroyed the ability to rescue the YPT1 mutation. Sequence analysis of
ypt1-complementing and -noncomplementing Ypt types suggests that surface loop3
represents a novel specificity domain of small G proteins.
FELDWISCH O, LAMMERTZ M, HARTMANN E, et al.
PURIFICATION
AND CHARACTERIZATION OF A CAMP-BINDING PROTEIN OF VOLVOX-CARTERI F NAGARIENSIS IYENGAR
EUR J BIOCHEM 228 (2): 480-489
Abstract:
Two cAMP-binding proteins, cbp1 and cbp2, were purified from the cytoplasm of
the green alga Volvox carteri. Both proteins have a native molecular
mass of 90 kDa as determined by gel filtration. cbp2 was purified to apparent
electrophoretic homogeneity, having a subunit molecular mass of 42 kDa as
determined by SDS/PAGE. The cbp1 preparation contains a 42-kDa and a 44-kDa
band. The cAMP-binding activity is not associated with protein kinase activity.
Tryptic peptides of cbp2 were sequenced by automated Edman degradation. Two
pairs of peptides differ in one amino acid only, thus pointing to the presence
of isoforms of cbp2. Both binding proteins differed from the cAMP-specific
phosphodiesterases of V. carteri with respect to charge, molecular mass and
binding affinity to N-6-cAMP-agarose, Reverse-phase chromatography of the bound
ligand revealed that the two binding proteins hydrolyse cAMP to 5'AMP. The
binding specificity of purified cbp1 and cbp2 was probed by a set of modified
cAMP derivatives. Both proteins bind cAMP strictly specifically in the anti
conformation; position 1 and 6 of the adenine moiety and at least one of the
exocyclic O atoms of the ribose cyclic phosphate moiety are essential.
3-Isobutyl-1-methylxanthine is an effective inhibitor of binding but the
natural methylxyanthines are not. At present it is not clear whether cbp1 and
cbp2 are individual proteins or isoforms of one another.
MILLER SM, KIRK DL
CHARACTERIZATION
OF A VOLVOX GENE REGULATING
ASYMMETRIC CELL-DIVISION
MOL BIOL CELL 6: 501-501 Suppl. S NOV 1995
1994
MA H
GTP-BINDING
PROTEINS IN PLANTS - NEW MEMBERS OF AN OLD FAMILY
PLANT MOL BIOL 26 (5): 1611-1636 DEC 1994
Abstract:
Regulatory guanine nucleotide-binding proteins (G proteins) have been studied extensively
in animal and microbial organisms, and they are divided into the heterotrimeric
and the small (monomeric) classes. Heterotrimeric G proteins are known to
mediate signal responses in a variety of pathways in animals and simple
eukaryotes, whiole small G proteins perform diverse functions including signal
transduction, secretion, and regulation of cytoskeleton. In recent years,
biochemical analyses have produced a large amount of information on the
presence and possible functions of G proteins in plants. Further, molecular
cloning has clearly demonstrated that plants have both heterotrimeric and small
G proteins. Although the functions of the plant heterotrimeric G proteins are
yet to be determined, expression analysis of an Arabidopsis Ga protein suggests
that it may be involved in the regulation of cell division and differentiation.
In contrast to the very few genes cloned thus far that encode heterotrimeric G
proteins in plants, a large number of small G proteins have been identified by
molecular cloning from various plants. In addition, several plant small G
proteins have been shown to be functional homologues of their counterparts in
animals and yeasts. Future studies using a number of approaches are likely to
yield insights into the role plant G proteins play.
VALIN P, GOULARD B, SANIELEVICI M
TOPOLOGY
DEPENDENCE IN LATTICE SIMULATIONS OF NONLINEAR PDES ON A MIMD COMPUTER
INT J MOD PHYS C 5 (6): 957-971 DEC 1994
Abstract:
We tested the parallelization of explicit schemes for the solution of
non-linear classical field theories of complex scalar fields which are capable
of simulating; hadronic collisions. Our attention focused on collisions in a
fractional model with a particularly rich inelastic spectrum of final states.
Relativistic collisions of all types were performed by computer on large
lattices (64 to 256 sites per dimension). The stability and accuracy of the
objects were tested by the use of two other methods of solutions:
Pseudo-spectral and semi-implicit. Parallelization of the Fortran code on a
64-transputer MIMD Volvox machine revealed, for certain topologies,
communication deadlock and less-than-optimum routing strategies when the number
of transputers used was less than the maximum. The observed speedup, for N
transputers in an appropriate topology, is shown to scale approximately as N,
but the overall gain in execution speed, for physically interesting problems,
is a modest 2-3 when compared to state-of-the-art workstations.
SCHULZE E, NAGEL S, GAVENIS K, et al.
STRUCTURALLY
DIVERGENT HISTONE H1 VARIANTS IN CHROMOSOMES CONTAINING HIGHLY CONDENSED
INTERPHASE CHROMATIN
J CELL BIOL 127 (6): 1789-1798 Part 2 DEC 1994
Abstract:
Condensed and late-replicating interphase chromatin in the Dipertan insect
Chironomus contains a divergent type of histone H1 with an inserted KAPKAP
repeat that is conserved in single H1 variants of Caenorhabditis elegans and Volvox
carteri. H1 peptides comprising the insertion interact specifically with DNA.
The Chironomid Glyptotendipes exhibits a corresponding correlation between the presence
of condensed chromosome sections and the appearance of a divergent H1 subtype.
The centromere regions and other sections of Glyptotendipes barbipes
chromosomes are inaccessible to immunodecoration by anti-H2B and anti-H1
antibodies one of which is known to recognize nine different epitopes in all
domains of the H1 molecule. Microelectrophoresis of the histones from manually
isolated unfixed centromeres revealed the presence of H1 and core histones. H1
genes of G. barpipes were sequenced and found to belong to two groups. H1 II
and H1 III are rather similar but differ remarkably from H1 I. About 30% of the
deduced amino acid residues were found to be unique to H1 I. Most conspicuous
is the insertion, SPAKSPGR, in H1 I that is lacking in H1 II and H1 III and at
its position gives rise to the sequence repeat SPAKSPAKSPGR. The homologous H1
I gene in Glyptotendipes salinus encodes the very similar repeat TPAKSPAKSPGR.
Both sequences are structurally related to the KAPKAP repeat in H1 I-1 specific
for condensed chromosome sites in Chironomus and to the SPKKSPKK repeat in sea
urchin sperm H1, lie at almost the same distance from the central globular
domain, and could interact with linker DNA in packaging condensed chromatin.
WOESSNER JP, MOLENDIJK AJ, VANEGMOND P, et al.
DOMAIN
CONSERVATION IN SEVERAL VOLVOCALEAN CELL-WALL PROTEINS
PLANT MOL BIOL 26 (3): 947-960 NOV 1994
Abstract:
Based on our previous work demonstrating that (SerPro)(x) epitopes are common
to extensin-like cell wall proteins in Chlamydomonas reinhardtii, we looked for
similar proteins in the distantly related species C. euganzetos. Using a
polyclonal antiserum against a (SerPro)(10) oligopeptide, we found distinct
sets of stage-specific polypeptides immunoprecipitated from in vitro
translations of C. eugametos RNA. Screening of a C. eugametos cDNA expression
library with the antiserum led to the isolation of a cDNA (WP6) encoding a
(SerPro)(x)-rich multidomain wall protein. Analysis of a similarly selected
cDNA (VSP-3) from a C. reinhardtii cDNA expression library revealed that it
also coded for a (SerPro)(x)-rich multidomain wall protein. The C-terminal rod
domains of VSP-3 and WP6 are highly homologous, while the N-terminal domains
are dissimilar; however, the N-terminal domain of VSP-3 is homologous to the
globular domain of a cell wall protein from Volvox carteri. Exon
shuffling might be responsible for this example of domain conservation over 350
million years of volvocalean cell wall protein evolution.
DIETMAIER W, FABRY S
ANALYSIS OF
THE INTRONS IN GENES ENCODING SMALL G-PROTEINS
CURR GENET 26 (5-6): 497-505 NOV-DEC 19
Abstract:
Because all small G proteins (SGPs) possess a very similar array of structural
and functional domains, they are obvious candidates for examining the
relationships postulated to exist between the exon-intron structure of genes
and the domain structure of the encoded proteins. To address this issue, and to
possibly gain insight into the evolution of their introns, we have analyzed
positions, sizes, and sequences of 125 introns from 28 SGP genes. These introns
were found to be distributed in 60 different locations throughout the aligned
sequences, with a preference for the 5'-half of the genes. More than 50% of the
positions were found to be shared by two or more genes, and genes encoding SGPs
of very similar amino acid sequence (i.e., isotypes) in quite closely related
species tend to have most, or all, of their introns in identical locations,
indicating a common evolutionary origin (homologous introns). However, with few
exceptions, no statistically significant sequence similarity or common folding
motif was found between homologous intron pairs. Only three intron positions
are shared between members of distantly related SGP subfamilies. These three
potentially ancient intron locations fall between regions encoding alpha-helices
or beta-sheets, but two of them interrupt regions encoding known functional
(guanosine-nucleotide-binding) modules. Intron positions that are occupied only
in single genes, or in genes encoding very similar SGPs, do not show any
preferential distribution with respect to regions encoding structural or
functional motifs. This discordance between exon modules and structural and/or
functional protein domains suggests that most, if not all, introns in modern
SGP genes arose by independent insertion events after diversification of the
various SGP subfamilies, and therefore probably did not participate in the
early evolution of these genes.
HALLMANN A, SUMPER M
REPORTER
GENES AND HIGHLY REGULATED PROMOTERS AS TOOLS FOR TRANSFORMATION EXPERIMENTS IN
VOLVOX-CARTERI
P NATL ACAD SCI USA 91 (24): 11562-11566 NOV 22 1994
Abstract:
The multicellular alga Volvox is an attractive model for the study of
developmental processes. With the recent report of successful transformation,
regulated promoters as well as reporter genes working in this organism are now
required. The Volvox genes encoding arylsulfatase and the extracellular
glycoprotein ISG are strictly regulated. The former is transcribed only under
conditions of sulfur starvation, whereas the latter operates under extreme
developmental control-i.e., it is transcribed for only a few minutes in Volvox
embryos at the stage of embryonic inversion. The gene encoding the sexual
pheromone of Volvox carteri was placed under the control of the
arylsulfatase promoter. In response to sulfur deprivation, V. carteri
transformed by this construct synthesized and secreted biologically active
pheromone. In addition, the gene encoding Volvox arylsulfatase was
placed under the control of the ISG promoter. Transformed algae synthesized
arylsulfatase mRNA only during embryonic inversion. These experiments
demonstrate the usefulness of both the arylsulfatase and the sexual.
WOESSNER JP, GOODENOUGH UW
VOLVOCINE
CELL-WALLS AND THEIR CONSTITUENT GLYCOPROTEINS - AN EVOLUTIONARY PERSPECTIVE
PROTOPLASMA 181 (1-4): 245-258 1994
Abstract:
Similarities in the composition of the extracellular matrix suggest that only
some species of the unicellular Chlamydomonas are closely related to the
colonial and multicellular flagellated members of the family Volvocaceae. The
cell walls from all of the algae in this volvocine group contain a crystalline
layer. This lattice structure can be used as a phylogenetic marker to divide
Chlamydomonas species into distinct classes, only one of which includes the
volvocacean algae. Similarly, not all species of Chlamydomonas are sensitive to
each other's cell wall lytic enzymes, implying divergence of the enzyme's inner
wall substrate. Interspecific reconstitution of the crystalline layer is
possible between C. reinhardtii and the multicellular Volvox carteri,
but not between C. reinhardtii and C. eugametos. The hydroxyproline-rich
glycoproteins (HRGPs) which make up the crystalline layer in genera which have
a similar crystal structure exhibit many homologies. Interestingly, the
evolutionarily distant cell walls of C. reinhardtii and C. eugametos also
contain some HRGPs displaying a few morphological and amino acid sequence
homologies. The morphological similarities between the flagellar agglutinins
(HRGPs responsible for sexual recognition and adhesion during the mating
reaction) and the cell wall HRGPs leads to the proposal of a superfamily from
which novel HRGPs (designed for self-assembly/recognition) can constantly
evolve. Just as Variations in the wall HRGPs can lead to unique wall
structures, new agglutinins facilitate sexual isolation of new species. Thus,
the HRGPs could emerge as Valuable phylogenetic markers.
HUBER O, SUMPER M
ALGAL-CAMS - ISOFORMS
OF A CELL-ADHESION MOLECULE IN EMBRYOS OF THE ALGA VOLVOX WITH HOMOLOGY TO DROSOPHILA FASCICLIN-I
EMBO J 13 (18): 4212-4222
Abstract:
Proof that plants possess homologs of animal adhesion proteins is lacking. In
this paper we describe the generation of monoclonal antibodies that interfere
with cell-cell contacts in the 4-cell embryo of the multicellular alga Volvox
carteri, resulting in a hole between the cells. The number of following cell
divisions is reduced and the cell division pattern is altered drastically.
Antibodies given at a later stage of embryogenesis specifically inhibit
inversion of the embryo, a morphogenetic movement that turns the embryo inside
out. Immunofluorescence microscopy localizes the antigen (Algal-CAM) at cell
contact sites of the
NASS N, MOKA R, JAENICKE L
ADENYLYL-CYCLASE
FROM THE GREEN-ALGA VOLVOX-CARTERI
F NAGARIENSIS - PARTIAL-PURIFICATION AND CHARACTERIZATION
AUST J PLANT PHYSIOL 21 (5): 613-622 1994
Abstract:
In order to understand changes in cyclic adenylate levels of Volvox
carteri during the process of sexual induction, we investigated the biochemical
properties of its membrane-bound adenylyl cyclase. Membrane preparations
possess low levels of Mg2+-dependent or Mn2+-dependent adenylyl cyclase
activity. This activity was solubilised and then purified 7800-fold. The enzyme
detergent complex has an apparent molecular mass of 100 kDa. Purified
preparations contain a major ATP-binding protein of 33 kDa as shown by affinity
labelling. The Mg2+-dependent basal enzyme activity is regulated by Ca2+, and
is highest in the presence of 10(-7) M Ca2+, but is inhibited by Ca2+ above
10(-5) M. La3+ at 10(-4) M also blocks activity. Neither calmodulin nor its
antagonists affect the enzyme activity, nor do the purified preparations
interact with immobilised calmodulin. Further mediators of G-protein action
(NaF, or GTP and its derivatives) and forskolins have no influence on the basal
activity of this plant enzyme. The function of adenylyl cyclase in sexual
induction of Volvox is discussed.
HOOPS HJ, LONG JJ, HILE ES
FLAGELLAR APPARATUS
STRUCTURE IS SIMILAR BUT NOT IDENTICAL IN VOLVULINA-STEINII, EUDORINA-ELEGANS,
AND PLEODORINA-ILLINOISENSIS (CHLOROPHYTA) - IMPLICATIONS FOR THE VOLVOCINE
EVOLUTIONARY LINEAGE
J PHYCOL 30 (4): 679-689 AUG 1994
Abstract:
The colonial and multicellular members of the Volvocales can be arranged in
order of increasing size and complexity as the ''volvocine series.'' This
series is often assumed to reflect an evolutionary progression. The flagellar
apparatuses of previously examined algae are not consistent with a simple
lineage. The flagellar apparatuses of Astrephomene gubernaculifera Pocock,
Gonium pectorale Muller, Platydorina caudata Kofoid, Volvox rousseletii
G. S. West, and V. carteri f. weismannia (Powers) Iyengar differ from one
another, and there is no apparent progression in flagellar apparatus features
from the simple to complex colonial forms. We examined the flagellar
apparatuses of Volvulina steinii Playfair, Eudorina elegans Ehr., and
Pleodorina illinoisensis Kofoid and found then to be similar to one another.
The basal bodies ave connected by a distal fiber that is offset to the anti
side of the cell. Two microtubular rootlets originate on the inside of the
basal bodies and extend toward the syn side. The other two rootlets are oriented
perpendicular to the first two and are anti-parallel to each other. A coarsely
striated component underlies the four-membered rootlets and extends to the
basal bodies. A proximal fiber complex connects the two basal bodies. This
complex consists of a branched striated component on the cis side of each basal
body. One part extends toward the anti side of the cell, while the other
extends into a fibrous component that runs between basal bodies. An additional
structure extends in the anti direction from the trans side of each basal body.
A fibrous component extends past one basal body in all four species. This
component goes past the trans basal body in Volvulina steinii and the cis basal
body in E. elegans and P. illinoisensis. The flagellar apparatuses of these
organisms are similar to those of G. pectorale and Volvox carteri but
different from the other colonial volvocalean algae examined. The algae
examined in this study plus G. pectorale and V. carteri probably share a common
evolutionary history that postdates the transition from the unicellular to
colonial habit. Such a shared evolutionary history is a requirement of the
volvocine hypothesis. However, we have not observed progressive changes in the
flagellar apparatus correlated with increasing cell number, differentiation,
and sexual specialization. Thus, it is possible, but not certain, that G.
pectorale, Volvulina steinii, E. elegans, P. illinoisensis, and Volvox
carteri may form part of a volvocine lineage.
KIRK DL
GERM-CELL
SPECIFICATION IN VOLVOX-CARTERI
CIBA F SYMP 182: 2-15 1994
Abstract:
Volvox carteri illustrates with diagrammatic clarity Weismann's concept
of an immortal germline that produces a mortal soma that will carry it for a
time, but then perish. Each V. carteri adult consists of about 16 asexual
reproductive cells (gonidia) in the interior of a sphere that consists at its
surface of about 2000 biflagellate somatic cells. When mature, each gonidium
divides to form a juvenile with this same cellular composition. Half-way
through their maturation, juveniles hatch out of the parenteral spheroid,
whereupon parental somatic cells undergo programmed death while juvenile
gonidia prepare for a new round of reproduction. The first visible step in V.
carteri germ-soma differentiation is asymmetric cleavage, which sets apart
large gonidial initials from small somatic initials. Experimental analysis
indicates that it is a difference in size, not any difference in cytoplasmic
quality, that determines whether a cell will become germinal or somatic.
Mutational and molecular studies lead to the following model for the genetic
control of the germ-soma dichotomy: first, the gls locus acts to cause asymmetric
division; then large cells activate a set of lag loci that suppress expression
of somatic genes, while small cells activate the regA locus that suppresses
gonidial genes.
SCHIEDLMEIER B, SCHMITT R, MULLER W, et al.
NUCLEAR
TRANSFORMATION OF VOLVOX-CARTERI
P NATL ACAD SCI
Abstract:
Stable nuclear transformation of Volvox carteri was achieved using the
cloned V. carteri nitA(+) gene (which encodes nitrate reductase) to complement
a nitA(-) mutation. Following bombardment of mutant cells with plasmid-coated
gold particles, putative transformants able to utilize nitrate as a nitrogen
source were recovered with an efficiency of approximate to 2.5 x 10(-5). DNA
analysis indicated that the plasmid integrated into the genome, often in
multiple copies, at sites other than the nitA locus. Cotransformants were
recovered with a frequency of 40-80% when cells were cobombarded with a selected
and an unselected marker. Thus, V. carteri becomes one of the simplest
multicellular organisms that is accessible to detailed molecular studies of
genes regulating cellular differentiation and morphogenesis.
KOUFOPANOU V
THE EVOLUTION
OF SOMA IN THE VOLVOCALES
AM NAT 143 (5): 907-931 MAY 1994
Abstract:
The presence of soma and the manner in which it segregates from the germ line
is a fundamental aspect of development. This article examines the origin and
evolution of soma in the Volvocales, the flagellated forms of green algae by
analyzing data on cell division and development of 370 species. Phylogenetic
analysis suggests that the cell wall is a preadaptation for the evolution of
large multicellular colonies with deterministic development. The allometry of
soma and germ supports the idea that soma functions to provide functional
flagella during the embryogenesis of large colonies (Volvocaceae). The need for
soma arises from a constraint that prevents simultaneous flagellation and cell
division of cells surrounded by rigid walls: basal bodies cannot remain
attached to their flagella while migrating to the mitotic poles. The
con-straint is different from those that may cause the separation of
flagellation and cell division in metazoan cells. Apart from a few
developmental variations, which may represent adaptations to larger size, the
Volvocaceae can be obtained by heterochronic changes in the timing of cell
division. Their small size compared to the size of nonflagellated relatives can
be attributed to their locomotion by flagella, which limits the maximum amount
of germ that can be carried by the soma. This limitation is manifested in a
negative correlation between size and number of germ cells among the largest
species of Volvocaceae (Volvox). the opposite of a positive one among
the smaller species.
NOZAKI H, ITOH M
PHYLOGENETIC-RELATIONSHIPS
WITHIN THE COLONIAL VOLVOCALES (CHLOROPHYTA) INFERRED FROM CLADISTIC-ANALYSIS
BASED ON MORPHOLOGICAL DATA
J PHYCOL 30 (2): 353-365 APR 1994
Abstract:
A cladistic analysis was used to deduce the phylogenetic relationships within the colonial Volvocales. Forty-one pairs of characters related to gross morphology and ultrastructure of vegetative colonies as well as asexual and sexual reproduction were analyzed based on parsimony, using the PAUP 3.0 computer program, for 25 species belonging to nine volvocacean and goniacean genera of the colonial Volvocales. Chlamydomonas reinhardtii Dangeard was the outgroup. The strict consensus tree indicated the presence of two monophyletic groups, one composed of all the volvocacean species analyzed in this study and the other containing the goniacean species except for the four-celled species Gonium sociale (Dujardin) Warming. In addition, these two groups constitute a large monophyletic group, to which G. sociale is a sister group. A new combination Tetrabaena socialis (Dujardin) Nozaki et Itoh and a new family Tetrabaenaceae Nozaki et Itoh are thus proposed for G. sociale. In addition, the analysis suggests that the volvocacean genera Eudorina and Pleodorina are paraphyletic groups, respectively, and that the monotypic genus Yamagishiella has no autapomorphic characters and represents primitive features of the anisogamous and oogamous genera of the Volvocaceae. Phylogenetic relationships within the Volvocaceae and the Goniaceae, as well as the various modes of sexual reproduction exhibited by these organisms, are discussed on the basis of the analysis.
HALLMANN A, SUMPER M
AN INDUCIBLE
ARYLSULFATASE OF VOLVOX-CARTERI
WITH PROPERTIES SUITABLE FOR A REPORTER-GENE SYSTEM - PURIFICATION,
CHARACTERIZATION AND MOLECULAR-CLONING
EUR J BIOCHEM 221 (1): 143-150 APR 1 1994
Abstract:
The multicellular green flagellate Volvox carteri synthesizes a
periplasmic arylsulfatase in response to sulfur deprivation. The inducible
enzyme has been purified to homogeneity and characterized. The corresponding
gene and cDNA have been cloned. Determination of the sequence of genomic clones
and comparisons to the cDNA sequence, revealed sixteen introns and seventeen a
exons that encode a 649-amino-acid polypeptide chain. Since the arylsulfatase
enzyme is readily assayed using chromogenic substrates, but is not detectable
in cells grown in sulfate-containing medium, the gene encoding arylsulfatase
may be useful as a reporter gene in V. carteri. In addition, the highly
regulated promoter of the arylsulfatase gene suggests its suitability as a tool
for producing inducible expression vectors for cloned genes.
SEKIMOTO H, SONE Y, FUJII T
REGULATION OF
EXPRESSION OF THE GENES FOR A SEX-PHEROMONE BY AN INDUCER OF THE SEX-PHEROMONE
IN THE CLOSTERIUM PERACEROSUM-STRIGOSUM-LITTORALE COMPLEX
PLANTA 193 (1): 137-144 MAR 1994
Abstract:
A sex pheromone, protoplast-release-inducing protein (PR-IP), of the Closterium
peracerosum-strigosum-littorale complex is known to induce the release of
protoplasts from mating-type minus (Mt(-)) cells during sexual reproduction and
to have two subunit polypeptides of 19 and 42 kDa. Here, we describe the
regulation mechanism for the release of the PR-IP. The sex pheromone was
fractionated to yield subunits of 19 and 42 kDa, respectively, and each subunit
was treated with V8 protease and with CNBr. By reference to the partial
amino-acid sequences of the digested polypeptides, oligo nucleotides were
synthesized and used as primers for the combined reverse
transcription-polymerase chain reaction. Amplified fragments of DNA, of 130 bp
in the case of the 19-kDa subunit and of 330 bp in the case of the 42-kDa
subunit, were obtained, sequenced, and used as probes to identify the
respective transcripts. From the results of Northern hybridization, the sizes
of transcripts were estimated to be 1.2 kb for the 18-kDa subunit and 1.4 kb
for the 42-kDa subunit. These transcripts appeared transiently only when
mating-type plus (mt(+)) cells were treated with another sex pheromone (PR-IP
Inducer) for more than 4h in the light. By immunoblotting with
anti-42-kDa-subunit antiserum, it was shown that PR-IP accumulated gradually in
the medium but not in the mt(+) cells after treatment with PR-IP Inducer in the
light. We suggest that PR-IP is synthesized de novo and secreted from mt(+)
cells only after the perception of PR-IP Inducer that has been released from
mt(-) cells in the light during the sexual reproduction of Closterium, An
analysis by genomic Southern hybridization revealed that probes for the 19-kDa
and 42-kDa peptides hybridized to 6.8-kb and 5.1-kb DNA fragments,
respectively, after the digestion of the genome with EcoRI. These hybridized
DNA fragments were obtained not only from the genome of mt(+) cells but also
from the genome of mt(-) cells, in which no transcripts for PR-IP could be
detected by Northern hybridization. On the basis of these results, we discuss
the possibility that the expression of the gene for the two subunits of PR-IP
might be critically dependent upon the action of putative sex-determining
genes.
SCHIEDLMEIER B, SCHMITT R
REPETITIOUS STRUCTURE
AND TRANSCRIPTION CONTROL OF A POLYUBIQUITIN GENE IN VOLVOX-CARTERI
CURR GENET 25 (2): 169-177 FEB 1994
Abstract:
Southern analysis indicated the presence of at least four ubiquitin gene loci
in the Volvox carteri genome. Three of these, a polyubiquitin gene
described here and a non-segregating ubiquitin gene pair, were assigned to two
different linkage groups by RFLP mapping; the non-polymorphic fourth gene locus
remained unassigned. The polyubiquitin gene was cloned and its 2,116-bp
sequence determined. It contains six exons each interrupted by an intron at
Gly35, and it encodes a pentameric polyubiquitin polypeptide consisting of five
runs of 76 identical amino-acid residues and a C-terminal extension of one
leucine. The five tandem repeats of coding units plus introns exhibit an
unusually high degree of overall sequence identity indicating an efficient
process of gene homogenization in this region of the V. carteri genome. S1
mapping revealed two closely-spaced transcription starts, 24 and 28 nucleotides
downstream from a putative TATA sequence. Preceding the TATA box are two 14-bp
conserved heat-shock elements (HSEs) and two octameric sequences closely
resembling an yeast HSE. Consistent with a 1.6-kb transcript seen on Northern
blots are two polyadenylation signals (TGTAA) located 99 bp and 169 bp
downstream from the TGA translational stop. The polyubiquitin gene was
transcribed throughout the Volvox life cycle with peaks in the 1.6-kb
mRNA levels during pre-cleavage, cleavage, and post-inversion. In contrast, an
0.6-kb monoubiquitin transcript was abundant only at the pre-cleavage stage
suggesting a different type of gene control. Heat shock increased the level of
polyubiquitin mRNA, whereas the level of monoubiquitin mRNA was down-regulated.
1993
KOUFOPANOU V,
SOMA AND GERM
- AN EXPERIMENTAL APPROACH USING VOLVOX
P ROY SOC LOND B BIO 254 (1340): 107-113
Abstract:
The separation of soma from germ may have originated as a result of a
specialization in source and sink, with somatic cells acting as sources,
gathering nutrients from the external environment and germ cells as sinks,
utilizing nutrients to grow and reproduce. This hypothesis can be tested in an
organism, such as Volvox, where single germ cells can be cultured in
isolation from the soma, thus serving both as source and sink, and their growth
compared with that of germ cells with an intact soma where source and sink are
separated into different cells. Results from such an experiment show that germ
cells grown with an intact soma had greater rates of increase than those grown
with disrupted soma or that were completely isolated, but the difference became
greater as nutrient concentration increased, as predicted by the
source-and-sink hypothesis. The advantage, however, was not sufficient to
compensate fully for the initial investment in soma, especially at low
nutrients, perhaps due to the energetic cost of swimming. In nature, species
with segregated soma are found in nutrient-rich lakes and ponds. In
experimental farm ponds, the biomass of such species increases with
eutrophication more than the biomass of related species without division of
labour, suggesting an advantage consistent with the source-and-sink.
MAIER I
GAMETE
ORIENTATION AND INDUCTION OF GAMETOGENESIS BY PHEROMONES IN ALGAE AND PLANTS
PLANT CELL ENVIRON 16 (8): 891-907 NOV 1993
Abstract:
This review attempts to give a concise overview of the widespread occurrence
and the significance, structure and function of pheromones in the chemical
communication between individuals of the same species during sexual
reproduction in algae and plants. Also included is information on the Oomyctes
and the chytridiomycete Allomyces. The terminology in respect of pheromone
function and pheromone-induced reactions is discussed.
VONGROMOFF ED, BECK CF
GENES
EXPRESSED DURING SEXUAL-DIFFERENTIATION OF CHLAMYDOMONAS-REINHARDTII
MOL GEN GENET 241 (3-4): 415-421 NOV 1993
Abstract:
Four genes specifically expressed during gametogenesis of Chlamydomonas
reinhardtii have been cloned and their expression patterns analyzed. mRNAs
encoded by these gamete-specific genes (gas) were absent or present only at
very low levels in vegetative cells and mature zygotes. In young zygotes 2 h
after gamete fusion, the mRNAs of three gas genes still persisted. The gas
mRNAs accumulated during gametic differentiation. The temporal patterns of
accumulation of individual mRNAs differed; some started to increase early
during gametogenesis, others accumulated in the late phase. The accumulation of
one of the late mRNAs (gas28) was stricly light-dependent. To illustrate the
utility of the genes cloned in the analysis of sexual differentiation in
Chlamydomonas reinhardtii we show that in a gametogenesis-defective mutant, the
expression of late genes is prevented while that of early genes is normal.
MEMON AR, HERRIN DL, THOMPSON GA
INTRACELLULAR
TRANSLOCATION OF A 28-KDA GTP-BINDING PROTEIN DURING OSMOTIC SHOCK-INDUCED
CELL-VOLUME REGULATION IN DUNALIELLA-SALINA
BIOCHIM BIOPHYS ACTA 1179 (1): 11-22
Abstract:
The primary aim of this study was to determine if small GTP-binding proteins
play a role in the conspicuous and much-examined volume control process in
Dunaliella salina. We confirmed the previous identification by Rodriguez et al.
(Rodriguez Rosales, M.P., Herrin, D.L. and Thompson, G.A., Jr. (1992) Plant
Physiol. 98, 446-451) of small GTP-binding proteins in the green alga
Dunaliella salina and revealed the presence of at least five such proteins,
having molecular masses of approx. 21, 28, 28.5, 29 and 30 kDa. These proteins
were concentrated largely in the endoplasmic reticulum (ER) and in an
intermediate density organelle fraction (GA) containing mainly Golgi vesicles,
mitochondria and flagella. The chloroplast fraction and plasma membrane
contained the 28-kDa GTP-binding protein exclusively, while the cytosol
contained both the 28-kDa component and small amounts of a 21-kDa GTP-binding
protein. Immunodetection analysis showed that the D. salina 28-kDa protein
cross-reacted strongly with a polyclonal antibody raised against a Volvox
carteri yptV1 type GTP-binding protein. This antibody was utilized for
quantitative GTP-binding protein measurements as described below. Certain
anti-GTP-binding protein antibodies derived from non-plant sources, namely,
monoclonal antibodies raised against yeast and mouse ypt1 GTP-binding proteins,
cross-reacted not only with the D. salina 28-kDa protein but also the 29-kDa
component. The 30-kDa GTP-binding protein of D. salina did not bind the
antibodies mentioned above but did cross-react with an anti-yeast ypt1
polyclonal antibody. None of the D. salina GTP-binding proteins reacted
positively with polyclonal antibodies raised against SEC4, rab1 or rab6
proteins. When D. salina cells were subjected to hypoosmotic swelling by
abruptly reducing the NaCl concentration of their medium from 1.7 M to 0.85 M,
the increase in cell surface area was accompanied by a substantial
translocation of the 28-kDa GTP-binding protein from the ER and GA fractions to
the plasma membrane, chloroplast and cytosolic fractions, as determined by
quantitative [P-32]GTP binding and [I-125]antibody binding on nitrocellulose
blots. This translocation increased the content of the 28-kDa component in the
plasma membrane, chloroplast and cytosol by 3-4-fold. No net movement of the
30-kDa GTP-binding protein from either the ER or GA fractions was observed
following hypoosmotic shock. We also examined the behavior of D. salina small
GTP-binding proteins following exposure of cells to hyperosmotic shock.
Increasing the NaCl concentration from 1.7 M to 3.4 M led within 8 min to a decrease
in 28-kDa GTP-binding protein content in ER, GA, plasma membrane and
chloroplasts, and a concurrent increase in the cytosol. The pattern of change
differed from that seen following hypoosmotic shock, where the plasma membrane
and chloroplast fractions, as well as the cytosol gained 28-kDa GTP-binding
protein during accelerated membrane vesicle trafficking. It appears that
hyperosmotic shock, by interrupting vesicular trafficking, releases the 28-kDa
GTP-binding proteins from their membrane associations. Two less abundant
GTP-binding proteins were also redistributed following hyperosmotic shock. A
30-kDa component of microsomes decreased in amount, but only after 8 min of
shock. And a barely detectable 21-kDa band present in organelle fractions was
slowly released into the cytosol, becoming relatively prominent there by 30
min. Our findings suggest a role for small GTP-binding proteins in
osmoregulatory volume control by D. salina.
KIRK MM, RANSICK A, MCRAE SE, et al.
THE
RELATIONSHIP BETWEEN CELL-SIZE AND CELL FATE IN VOLVOX-CARTERI
J CELL BIOL 123 (1): 191-208 OCT 199
Abstract:
In Volvox carteri development, visibly asymmetric cleavage divisions set
apart large embryonic cells that will become asexual reproductive cells
(gonidia) from smaller cells that will produce terminally differentiated
somatic cells. Three mechanisms have been proposed to explain how asymmetric
division leads to cell specification in Volvox: (a) by a direct effect
of cell size (or a property derived from it) on cell specification, (b) by
segregation of a cytoplasmic factor resembling germ plasm into large cells, and
(c) by a combined effect of differences in cytoplasmic quality and cytoplasmic
quantity. In this study a variety of V carteri embryos with genetically and
experimentally altered patterns of development were examined in an attempt to
distinguish among these hypotheses. No evidence was found for regionally
specialized cytoplasm that is essential for gonidial specification. In all
cases studied, cells with a diameter > approximately 8 mum at the end of
cleavage-no matter where or how these cells had been produced in the
embryo-developed as gonidia. Instructive observations in this regard were
obtained by three different experimental interventions. (a) When heat shock was
used to interrupt cleavage prematurely, so that presumptive somatic cells were
left much larger than they normally would be at the end of cleavage, most cells
differentiated as gonidia. This result was obtained both with wild-type embryos
that had already divided asymmetrically (and should have segregated any
cytoplasmic determinants involved in cell specification) and with embryos of a
mutant that normally produces only somatic cells. (b) When individual wild-type
blastomeres were isolated at the 16-cell stage, both the anterior blastomeres
that normally produce two gonidia each and the posterior blastomeres that
normally produce no gonidia underwent modified cleavage patterns and each
produced an average of one large cell that developed as a gonidium. (c) When
large cells were created microsurgically in a region of the embryo that
normally makes only somatic cells, these large cells became gonidia. These data
argue strongly for a central role of cell size in germ/soma specification in Volvox
carteri, but leave open the question of how differences in cell size are
actually transduced into differences in gene expression.
FABRY S, JACOBSEN A, HUBER H, et al.
STRUCTURE,
EXPRESSION, AND PHYLOGENETIC-RELATIONSHIPS OF A FAMILY OF YPT GENES ENCODING
SMALL G-PROTEINS IN THE GREEN-ALGA VOLVOX-CARTERI
CURR GENET 24 (3): 229-240 SEP 1993
Abstract:
In addition to the previously described gene yptV1 encoding a small G-protein
we have now identified and sequenced four more ras-related ypt genes
(yptV2-yptV5) from the green alga Volvox carteri. The four new genes
encode polypeptides consisting of 203 to 217 amino-acid residues that contain
the typical sequence elements (GTP-binding domains, effector domain) of the
ypt/rab subgroup of the Ras superfamily. Comparison of the derived amino-acid
sequences from the V carteri ypt gene products and their Ypt homologs from
other species revealed similarity values ranging from 60% to 85%, whereas
intraspecies similarities were found to approach only 55%. The coding sequences
are interrupted by 5-7 introns of variable size (70-1000 nucleotides) occupying
different positions in the genes. Reverse-transcribed samples of stage-specific
RNAs were PCR-amplified with primers specific to yptV1, yptV3, yptV4, and yptV5
to determine if yptV transcription might be restricted to either cell type or to
a specific stage of the life cycle. These experiments demonstrated that each of
these genes is expressed throughout the entire Volvox life cycle and in
both the somatic and the reproductive cells of the alga. The transcription start
sites of yptV1 and yptV5 were mapped by primer extension. Expression of
recombinant yptV cDNA in E. coli yielded recombinant proteins that bound GTP
specifically, demonstrating a property which is typical for small G-proteins.
The derived YptV polypeptide sequences were used to group them into four
distinct classes of Ras-like proteins. These are the first proteins of the Ras
superfamily to be identified in a green alga. We discuss the possible. role of
the YptV-proteins in the intracellular vesicle transport of Volvox.
MILLER SM, SCHMITT R, KIRK DL
JORDAN, AN
ACTIVE VOLVOX TRANSPOSABLE
ELEMENT SIMILAR TO HIGHER-PLANT TRANSPOSONS
PLANT CELL 5 (9): 1125-1138 SEP 1993
Abstract:
We have isolated a 1595-bp transposable element from the multicellular green
alga Volvox carteri following its insertion into the nitrate reductase
(nitA) locus. This element, which we have named
HSU JP, HSU WC, TSAO HK
DIFFUSION-ENHANCED
BIOREACTIONS - A HYPOTHETICAL MECHANISM FOR PLANT-CELL AGGREGATION
B MATH BIOL 55 (5): 869-889 SEP 1993
Abstract:
We show that the existence of diffusional resistance due to the presence of a
solid phase can have a positive effect on the metabolic reactions of plant
cells. In this case the efficiency of metabolic reactions, defined as the ratio
of rate of production of biomass of aggregated cells/rate of production of
biomass of dispersed cells. can be greater than unity for a certain range of
aggregate sizes for both so[id spheres (common plant cell aggregates) and
hollow spheres (e.g. Volvox aggregates). This means that, under
appropriate conditions, plant cells tend to stay in the aggregated form to
improve the efficiency of their metabolic reactions. The result of the present
analysis provides an explanation as to why aggregates of plant cells are
observed under typical culture conditions.
LINDAUER A, MULLER K, SCHMITT R
2 HISTONE
H1-ENCODING GENES OF THE GREEN-ALGA VOLVOX-CARTERI
WITH FEATURES INTERMEDIATE BETWEEN PLANT AND ANIMAL GENES
GENE 129 (1): 59-68
Abstract:
Southern hybridization indicated the presence of at least two and possibly four
histone H1-encoding genes occurring as singlets in the Volvox carteri
genome. Two of these genes, H1-I and H1-II, have been cloned and characterized.
Their coding sequences are each interrupted by three introns, but only the
position of the second intron is identically conserved in both H1-I and H1-II.
The encoded 260-amino-acid (aa) (H1-1) and 240-aa (H1-II) polypeptides possess
the typical tripartite organization of animal H1 histones, with variable N- and
C-terminal domains flanking a conserved 'globular' DNA-binding domain.
Extensive differences in their variable regions suggest that H1-I and H1-II(62%
identity) represent two isotypes with different functions. A prominent
KAPKAP-KAA motif in the H1-I N-terminal region, similarly seen in single H1
variants of a mosquito and a nematode, has a putative function in packing
condensed subtypes of chromatin. Different from higher plants, but like
animals, the H1 genes of V. carteri possess a typical 3' palindrome for mRNA
processing, resulting in non-polyadenylated mRNAs. Transcription initiates 33
nucleotides (nt) (H1-I) and 26 nt (H1-II) downstream of typical TATA boxes. A
putative 20-bp conserved enhancer element upstream of each TATA box closely
resembles the consensus sequence associated with the nucleosomal
histone-encoding genes in V. carteri [Muller et al., Gene 93 (1990) 167-175]
and suggests stringent regulation. Accordingly, transcription of H1 was shown
to be restricted to late embryogenesis, when new flagella are produced. We
discuss the inferred accessory role of histone H1 proteins in stabilizing
axonemal microtubules, as has been recently observed in sea urchin flagella
[Multigner et al., Nature 360 (1992) 33-39].
WAFFENSCHMIDT S, WOESSNER JP, BEER K, et al.
ISODITYROSINE
CROSS-LINKING MEDIATES INSOLUBILIZATION OF CELL-WALLS IN CHLAMYDOMONAS
PLANT CELL 5 (7): 809-820 JUL 1993
Abstract:
Enzymatic removal of the cell wall vegetative Chlamydomonas reinhardtii cells
to transcribe wall genes and synthesize new hydroxyproline-rich glycoproteins
(HRGPs) related to the extensins found in higher plant cell walls. A cDNA
expression library made from such induced cells was screened with antibodies to
an oligopeptide containing the (SP)x repetitive domains found in Chlamydomonas
wall proteins. One of the selected cDNAs encodes an (SP)x-rich polypeptide that
also displays a repeated YGG motif Ascorbate, a peroxidase inhibitor, and
tyrosine derivatives were shown to inhibit insolubilization of both the
vegetative and zygotic cell walls of Chlamydomonas, suggesting that oxidative
cross-linking of tyrosines is occurring. Moreover, insolubilization of both
walls was concomitant with a burst in H2O2 production and in extracellular
peroxidase activity. Finally, both isodityrosine and dityrosine were found in
hydrolysates of the insolubilized vegetative wall layer. We propose that the
formation of tyrosine cross-links is essential to Chlamydomonas HRGP
insolubilization.
DESNITSKI AG
ON THE ORIGINS AND EARLY EVOLUTION
OF MULTICELLULARITY
BIOSYSTEMS 29 (2-3): 129-132 1993
Abstract:
In this paper an attempt is made to consider the significance of recent data on
the organization and development of Volvox, a multicellular spheroidal
green alga, for the unsolved problem of metazoan origins. A brief analysis is
made of differences and similarities in some trends and principles during the
establishment of metazoan and volvocalean multicellularity.
FODINGER M, ORTNER S, PLAIMAUER B, et al.
PATHOGENIC
ENTAMOEBA-HISTOLYTICA - CDNA CLONING OF A HISTONE H3 WITH A DIVERGENT PRIMARY
STRUCTURE
MOL BIOCHEM PARASIT 59 (2): 315-322 JUN 1993
Abstract:
Entamoeba histolytica has an unusual nuclear structure characterized by a low
degree of chromatin condensation and the absence of stainable metaphase
chromosomes. Although nucleosome-like particles were observed, no information
about histones was available so far. In this paper we describe a cDNA clone
with significant homology to H3 histones that was isolated from a library of
pathogenic E. histolytica.
The complete cDNA encodes a 15-kDa polypeptide, which like the histone sequence from Volvox carteri is shorter by one residue than the human homologue. The amino acid sequence has only 69% identity with human H3.3 histone and 67% identity with the human H3.1 histone. This is the highest degree of sequence divergence observed for any eukaryote H3 histone sequence. Our results indicate that this divergence may contribute to the unusual chromatin structure of E. histolytica.
JOSHI S, MILLER MI
MAXIMUM A POSTERIORI
ESTIMATION WITH GOOD ROUGHNESS FOR 3-DIMENSIONAL OPTICAL-SECTIONING MICROSCOPY
J OPT SOC AM A 10 (5): 1078-1085 MAY 1993
Abstract:
The three-dimensional image-reconstruction problem solved here for optical-sectioning
microscopy is to estimate the fluorescence intensity lambda(x), where x
is-an-element-of R3, given a series of Poisson counting process measurements
{M(j)(dx)}j=1J, each with intensity s(j)(y) integral(R3)p(j)(y\x)lambda(x)dx,
with p(j)(y\x) being the point spread of the optics focused to the jth plane
and s(j)(y) the detection probability for detector point y at focal depth j. A
maximum a posteriori reconstruction generated by inducing a prior distribution
on the space of images via Good's three-dimensional rotationally invariant
roughness penalty integral(R3)[\DELTAlambda(x)\2/lambda(x)]dx. It is proven
that the sequence of iterates that is generated by using the expectation
maximization algorithm is monotonically increasing in posterior probability,
with stable points of the iteration satisfying the necessary maximizer
conditions of the maximum a posteriori solution. The algorithms were
implemented on the DECmpp-SX, a 64 x 64 parallel processor, running at <2
s/(64(3), 3-D iteration). Results are demonstrated from simulated as well as
amoebae and volvox data. We study performance comparisons of the
algorithms for the missing-data problems corresponding to fast data collection
for rapid motion studies in which every other focal plane is removed and for
imaging with limited detector areas and efficiency.
LINDAUER A, FRASER D, BRUDERLEIN M, et al.
REVERSE-TRANSCRIPTASE
FAMILIES AND A COPIA-LIKE RETROTRANSPOSON, OSSER, IN THE GREEN-ALGA VOLVOX-CARTERI
FEBS LETT 319 (3): 261-266
Abstract:
By using the polymerase chain reaction (PCR) we have isolated and sequenced two
distinct families of reverse transcriptase (RT) sequences from the genome of
the colonial alga, Volvox carteri. Probing a genomic library with these
RT clones revealed copia-like retrotransposons. One of these elements, named
Osser, is 4,875 bp long, bordered by 197-bp identical long terminal repeats
(LTRs), and shows the typical organization of retrotransposons belonging to the
copia-Ty1 group. This is the first complete copia-like retrotransposon sequence
described in a green alga.
SUMPER M, BERG E, WENZL S, et al.
HOW A
SEX-PHEROMONE MIGHT ACT AT A CONCENTRATION BELOW 10(-16) M
EMBO J 12 (3): 831-836 MAR 1993
Abstract:
The sex-inducing pheromone of Volvox carteri is a glycoprotein that
triggers development of males and females at a concentration below 10(-16) M.
Evidence is presented for the existence of a novel mechanism of signal
amplification operating within the extracellular matrix of this multicellular
organism. A family of 70 kDa matrix glycoproteins denoted pherophorins bear a
C-terminal domain being homologous to the sex-inducing pheromone. Under the
influence of the pheromone, this domain is liberated by highly specific
proteolysis.
SEKIMOTO H, SATOH S, FUJII T
ANALYSIS OF
BINDING OF BIOTINYLATED PROTOPLAST-RELEASE-INDUCING PROTEIN THAT INDUCES
RELEASE OF GAMETIC PROTOPLASTS IN THE CLOSTERIUM-PERACEROSUM-STRIGOSUM-LITTORALE
COMPLEX
PLANTA 189 (3): 468-474 MAR 1993
Abstract:
A protoplast-release-inducing protein (PR-IP) which is released from
mating-type plus (mt+) cells and induces the release of gametic protoplasts
from mating-type minus (mt-) cells of Closterium was biotinylated and then used
to examine the interaction of this protein with mt- cells. The
protoplast-release-inducing activity of PR-IP was not altered after the
biotinylation. When mt- cells that had been pre-cultured for 24 h were
incubated with biotinylated PR-IP for 6 h in nitrogen-deficient medium that
contained 1 % (w/v) bovine serum albumin, and then washed with the same medium,
only a 19-kDa polypeptide, the smaller subunit of PR IP, was detected in cells
by the avidin and biotinylated horseradish-peroxidase macromolecular complex
system. The amount of bound 19-kDa polypeptide increased with increasing doses
of PR-IP and reached a maximum at around 10 nM, reflecting the
protoplast-release-inducing activity. From a Scatchard plot, the dissociation
constant of the polypeptide was calculated to be 2.7 . 10(-8) M. The binding of
the polypeptide proceeded only after an appropriate period of pre-culture in
the light, and the polypeptide was competitively displaced by non-biotinylated
PR-IP. From these results, it appears that the PR-IP induces the release of
protoplasts from mt- cells by binding of a polypeptide of relative molecular
mass 19000 to the receptor on the cell surface in a manner analogous to the
binding of peptide hormones in animals.
KIM GH, FRITZ L
A SIGNAL
GLYCOPROTEIN WITH ALPHA-D-MANNOSYL RESIDUES IS INVOLVED IN THE WOUND-HEALING
RESPONSE OF ANTITHAMNION-SPARSUM (CERAMIALES, RHODPHYTA)
J PHYCOL 29 (1): 85-90 FEB 1993
Abstract:
A variety of fluorescein isothiocyanate-labeled lectins specific for different
sugar moieties were examined as probes for the wound-healing response in the
filamentous red alga Antithamnion sparsum Tokida. Among them, only concanavalin
A (ConA) and Lens culrinaris agglutinin (LCA), which have specificity to
alpha-D-mannosyl residues, bound specifically to repair cells during the
wound-healing process. When ConA or LCA was added at various time intervals
after wounding, it first bound (3 h post-wounding) as a thin layer at the tips
of the adjacent cells. Later (4-5 h post-wounding) labeling also appeared at
the tips of the repair cells. Intense labeling at these sites continued
throughout the healing process until repair cell fusion, at which time the
lectin labeling was reduced to a narrow ring around the area of fusion. When
added to plants prior to wounding and continually monitored, these same lectins
acted as inhibitors to the wound-healing response. Other control lectins showed
no inhibitory effects. A crude extract solution obtained from decapitated
filaments stimulated the wound-healing response, and a lectin-binding component
bound strongly to a protein-binding transfer membrane. These results suggest
that the labeled compound is a glycoprotein that has alpha-D-mannosyl residues
and is similar to the repair hormone rhodomorphin found in Griffithsia
HOOPS HJ
FLAGELLAR,
CELLULAR AND ORGANISMAL POLARITY IN VOLVOX-CARTERI
J CELL SCI 104: 105-117 Part
Abstract:
It has previously been shown that the flagellar apparatus of the mature Volvox
carteri somatic cell lacks the 180-degrees rotational symmetry typical of most
unicellular green algae. This asymmetry has been postulated to be the result of
rotation of each half of the flagellar apparatus. Here it is shown that V.
carteri axonemes contain polarity markers that are similar to those found in
Chlamydomonas, except that in V. carteri the number one doublets do not face
each other as they do in Chlamydomonas but are oriented in parallel and at
approximately right angles to the line that connects the flagella. Thus, the
rotational orientations of the axonemes are consistent with the postulate that
the flagella of V. carteri have rotated in opposite directions, as was
predicted earlier from the positions of the basal fibers and microtubular
rootlets. Moreover, high-speed cinephotomicrographic analysis shows that the V.
carteri flagellar effective strokes are also oriented in approximately the same
direction, and in parallel planes. These results suggest that the direction of
the effective stroke in both Chlamydomonas and Volvox is fixed, and that
rotation of the axoneme is the cause of the differences in flagellar motility
observed between Chlamydomonas and Volvox. These differences are
probably essential for effective organismal motility. Cellular polarity of V.
carteri can be related to that of Chlamydomonas after taking into account the
developmental reorientation of flagellar apparatus components. This
reorientation also results in the movement of the eye-spot from a position
nearer one of the flagellar bases to a position approximately equidistant
between them. By analogy to Chlamydomonas, the anti side of the V. carteri
somatic cell faces the spheroid anterior, the syn side faces the spheroid
posterior. The cis side of the cell is to the cell's left (the right to an
outside observer), although it cannot be described solely on the basis of
eyespot position as it can in Chlamydomonas, while the trans side is to the
cell's right It follows that if the direction of the effective flagellar stroke
is specified by structural features, then effective organismal motility in V.
carteri, will be accomplished only if the cells are held in the proper
orientation with respect to one another. The simplest arrangement that will
yield both progression and rotation in ovoid or spherical colonies composed of biflagellate
isokont cells is one in which the cells are arranged with rotational symmetry
about the anterior-posterior axis of the spheroid. Analysis of the polarity of
somatic cells from throughout the spheroid shows that it is constructed with
just such symmetry. This symmetry probably originates with the very first
divisions.
JAENICKE L, FELDWISCH O, MERKL B, et al.
EXPRESSION OF
HIGHLY-ACTIVE SEX-INDUCING PHEROMONE OF VOLVOX-CARTERI
F NAGARIENSIS IN A MAMMALIAN-CELL SYSTEM
FEBS LETT 316 (3): 257-260
Abstract:
A cDNA fragment coding for the sex-inducing glycoprotein of Volvox
carteri f. nagariensis was expressed in a mammalian cell system (baby hamster
kidney (BHK) cells). The transfection product exhibited a specific biological
activity intermediate between the natural pheromone of the strains Volvox
carteri f. nagariensis and Volvox carteri f. weismannia. Immunoblot analysis
showed that the sex-inducing activity was expressed as a set of three
iso-glycoproteins (35, 34 and 31 kDa).
DENIS H, LACROIX JC
THE DICHOTOMY
BETWEEN GERM LINE AND SOMATIC LINE, AND THE ORIGIN OF CELL MORTALITY
TRENDS GENET 9 (1): 7-11 JAN 1993
Abstract:
The germ cells of extant animals are potentially immortal, whereas somatic
cells are mortal, that is, they are able to carry out only a finite number of
divisions. In this article we propose an evolutionary interpretation of these
differences. We assume that germ cells of the earliest metazoans inherited
immortality from their unicellular ancestor, while somatic cells acquired
mortality by gaining new functions. It follows that cell mortality was under
genetic control from the beginning of metazoan life.
HOLLOWDAY ED
CEPHALODELLA-EDAX
SP-NOV A ROTIFER PARASITIC IN THE MOTILE COLONIAL ALGA UROGLENA-VOLVOX EHRENBERG
HYDROBIOLOGIA 255: 445-448 APR 16 1993
1992
DUBOUX T, FERREIRA A, GASTALDO M
MIMD
DICTIONARY MACHINES - FROM THEORY TO PRACTICE
LECT NOTES COMPUT SC 634: 545-550 1992
Abstract:
We describe the implementation of a dictionary structure on a distributed
memory parallel computer. The dictionary is an important data structure used in
applications such as sorting and searching, symbol-table and index-table
implementations. Theoretical as well as practical aspects of the development of
the application are discussed. Our target machine was a Volvox IS860
with 8 nodes, each composed of one Transputer T800 from INMOS plus an Intel
i860. Extensive testing was carried out and the results reported. We also
address problems and solutions connected to the programming environment of such
a machine
BOWSER SS, ALEXANDER SP,
EXTRACELLULAR-MATRIX
AUGMENTS MECHANICAL-PROPERTIES OF PSEUDOPODIA IN THE CARNIVOROUS FORAMINIFERAN
ASTRAMMINA-RARA - ROLE IN PREY CAPTURE
J PROTOZOOL 39 (6): 724-732 NOV-DEC 1992
Abstract:
The seemingly delicate, strand-like pseudopodia of Astrammina rara, a
camivorous benthic foraminiferan, adhere to and withstand the rigorous
movements of meiofaunal prey. Previous electron microscopic studies identified
two novel structures that might account for the unusual tensile properties of
these pseudopodia: 1) an extensive, coiled microtubule cytoskeleton and 2) a
fibrous extracellular matrix vesting the pseudopodial surface. In the present
study, we found that pseudopodial networks microsurgically removed from A.
rara's cell body captured Artemia metanauplii as efficiently as intact
organisms, and therefore used them to test the role of microtubules and
extracellular matrix components in augmenting pseudopodial strength. Agents
that specifically disassemble microtubules (1 mM colchicine or 20 muM
nocodazole) or generally disrupt pseudopodial integrity (heat, 10 mM
formaldehyde, 1 mg/ml saponin) failed to inhibit prey capture. All of these
treatments left the extracellular matrix intact as revealed by
immunofluorescence and scanning electron microscopy. The elastic and tensile
properties of the extracellular matrix, isolated by solubilization of
pseudopodial cytoplasm using the nonionic detergent Triton X-100, were similar
to those of intact pseudopodial networks when assayed with calibrated
microneedles or a flexible rubber substrate. These observations indicate that
A. rara uses a fibrous extracellular matrix to augment cytoplasmic tensile
properties.
MISHRA SR, SHARMA S, YADAV RK
PHYTOPLANKTONIC
COMMUNITIES IN RELATION TO ENVIRONMENTAL-CONDITIONS OF LENTIC WATERS AT GWALIOR
(MP)
J ENVIRON BIOL 13 (4): 291-296 OCT 1992
Abstract:
A study was undertaken to determine the distribution of phytoplanktonic
communities in two lentic water bodies of variable nature in
FABRY S, NASS N, HUBER H, et al.
THE YPTV1
GENE ENCODES A SMALL G-PROTEIN IN THE GREEN-ALGA VOLVOX-CARTERI - GENE STRUCTURE AND PROPERTIES OF THE GENE-PRODUCT
GENE 118 (2): 153-162
Abstract:
Small G-proteins encoded by ras-like genes are ubiquitous in eukaryotic cells.
These G-proteins are believed to play a role in central processes, such as
signal transduction, cell differentiation and membrane vesicle transport. By
screening genomic and cDNA libraries of the colonial alga, Volvox
carteri f. nagariensis, with ypt DNA probes from Zea mays, we have identified
the first member of a ypt gene family, yptV1, within a green alga. The 1538-bp
yptV1 gene of V. carteri consists of nine exons and eight introns and has three
potential polyadenylation sites 210, 420 and 500 bp downstream from the UGA
stop codon. The derived 203-amino-acid polypeptide, YptV1, exhibits 81%
similarity with Ypt1 from mouse, with the corresponding genes sharing four
identical intron positions. Recombinant YptV1 (reYptV1) produced in Escherichia
coli retains the ability to bind GTP after SDS-PAGE and immobilization on
nitrocellulose. Immunological studies using polyclonal antibodies against
reYptV1 indicate that the protein is present in the membrane fraction of a V.
carteri extract and is expressed throughout the whole life-cycle of the alga.
Similar to other Ras-like proteins, YptV1 contains two conserved C-terminal
cysteine residues suggesting post-translational modification(s), such as
isoprenylation or palmitoylation, required for membrane anchoring. The
presumptive role of YptV1 in cytoplasmic vesicle transport is briefly
discussed.
VOYTAS DF, CUMMINGS MP, KONIECZNY A, et al.
COPIA-LIKE
RETROTRANSPOSONS ARE UBIQUITOUS AMONG PLANTS
P NATL ACAD SCI
Abstract:
Transposable genetic elements are assumed to be a feature of all eukaryotic
genomes. Their identification, however, has largely been haphazard, limited
principally to organisms subjected to molecular or genetic scrutiny. We
assessed the phylogenetic distribution of copia-like retrotransposons, a class
of transposable element that proliferates by reverse transcription, using a
polymerase chain reaction assay designed to detect copia-like element reverse
transcriptase sequences. copia-like retrotransposons were identified in 64
plant species as well as the photosynthetic protist Volvox carteri. The
plant species included representatives from 9 of 10 plant divisions, including
bryophytes, lycopods, ferns, gymnosperms, and angiosperms. DNA sequence
analysis of 29 cloned PCR products and of a maize retrotransposon cDNA
confirmed the identity of these sequences as copia-like reverse transcriptase
sequences, thereby demonstrating that this class of retrotransposons is a
ubiquitous component of plant genomes.
DOMOZYCH DS, WELLS B, SHAW PJ
THE CELL-WALL
OF THE CHLAMYDOMONAD FLAGELLATE, GLOEOMONAS-KUPFFERI (VOLVOCALES, CHLOROPHYTA)
PROTOPLASMA 168 (3-4): 95-106 1992
Abstract:
The large unicellular flagellate, Gloeomonas kupfferi, has recently been used
as an important tool in chlamydomonad cell biology research, especially in
studies dealing with the structure and function of the endomembrane system.
However, little is known about the main secretory product, the cell wall. This
study presents structural, chemical and immunological information about this
wall. This 850-900 nm thick matrix is highly elaborate and consists of three
distinct layers: an inner stratum (325 nm thick) consisting of tightly
interwoven fibers, a medial crystalline layer consisting of 22-23 nm subunits
and an outer wall layer (500 nm thick) of outwardly-radiating fibrils. Rapid
freeze-deep etch analysis reveals that the 35-40 nm fibers of the outer layer form
a quasi-lattice of 160 nm subunits. The outer wall can be removed from whole
pellets using the chelator, CDTA. The medial wall complex can be solubilized by
perchlorate. SDS-gel electrophoresis reveals that the perchlorate
soluble-material consists of five high molecular weight glycoproteins and five
major low molecular weight glycoproteins. The electrophoretic profile is
roughly similar to that of Chlamydomonas reinhardtii. Antibodies were
successfully raised against the outer wall component and were shown to label
the outer wall layer.
BUCHHEIM MA, CHAPMAN RL
PHYLOGENY OF
CARTERIA (CHLOROPHYCEAE) INFERRED FROM MOLECULAR AND ORGANISMAL DATA
J PHYCOL 28 (3): 362-374 JUN 1992
Abstract:
Comparative ultrastructural data have shown that at least two distinct groups
exist within Carteria. Similarly, interpretations of variation in gross
morphological features have led to the discovery of morphologically distinct
groups within the genus. Partial sequences from the nuclear-encoded small- and
large-subunit ribosomal RNA molecules of selected Carteria taxa were studied as
a means of 1) testing hypotheses that distinct groups of species exist within
the genus and 2) assessing monophyly of the genus. Parsimony analysis of the
sequence data suggests that three Carteria species, C. lunzensis, C. crucifera,
and C. olivieri, form a monopkyletic group that is the basal sister group to
all other ingroup flagellate taxa (including species of Chlamydomonas,
Haematococcus, Stephanosphaera, Volvox, and Eudorina). Two other
Carteria taxa, C. radiosa and Carteria sp. (UTEX isolate LB 762), form a clade
that is the sister group to a clade that includes Haematococcus spp., Chlamydomonas
spp., and Stephanosphaera. Thus, the sequence data support the interpretations
of ultrastructural evidence that described two distinct Carteria lineages.
Moreover, the sequence data suggest that these two Carteria groups do not form
a monophyletic assemblage. Parsimony analysis of a suite of organismal
(morphological, ultrastructural, life history, and biochemical) character data
also suggest two distinct lineages among the five Carteria taxa; however, the
organismal data are ambiguous regarding monophyly of these Carteria taxa. When
the two independent data sets are pooled, monophyly of Carteria is not
supported; therefore, the weight of available evidence, both molecular and
organismal, fails to support the concept of Carteria as a natural genus.
BLAKEFIELD MK, CALKINS J
INHIBITION OF
PHOTOTAXIS IN VOLVOX-AUREUS BY
NATURAL AND SIMULATED SOLAR ULTRAVIOLET-LIGHT
PHOTOCHEM PHOTOBIOL 55 (6): 867-872 JUN 1992
Abstract:
Exposure to artificial UV wavelengths and the UV component of sunlight delays
positive phototaxis in the green alga Volvox aureus. Broad band
wavelength filters were used to modify the Output from UV-B sources (280-320
nm) and natural sunlight. The delay in phototaxis by artificial UV is increased
with exposure to shorter UV-B wavelengths. Natural sunlight experiments were
performed with exposure to full sunlight and to its UV component only. The UV component
present in summer sunlight Produced long periods of inhibition in phototaxis
and even lethality, while exposure to the total spectrum of sunlight had no
significant effects on movement or survival. The data indicate that although
this species of alga is well equipped to deal with present levels of UV
exposure, increases in the short UV-B wavelengths in sunlight may force an
alteration in patterns of photomovement.
ERTL H, HALLMANN A, WENZL S, et al.
A NOVEL
EXTENSIN THAT MAY ORGANIZE EXTRACELLULAR-MATRIX BIOGENESIS IN VOLVOX-CARTERI
EMBO J 11 (6): 2055-2062 JUN 1992
Abstract:
ISG is a sulphated, extracellular glycoprotein synthesized for only a few minutes
in inverting Volvox embryos and inverting sperm cell packets. This
control operates at the level of transcription. ISG has been characterized by
studies of protein chemistry and electron microscopy. The primary structure of
ISG has been derived from genomic DNA and cDNA. ISG is composed of a globular
and a rod-shaped domain. The rod-shaped domain represents a member of the
extensin family with numerous repeats of Ser-(Hyp)4-6 motifs. A synthetic
decapeptide matching the C-terminal sequence is able to disaggregate the
organism into individual cells. Immunofluorescence microscopy localizes ISG
within the boundary zone of the ECM.
DESNITSKI AG
CELLULAR
MECHANISMS OF THE EVOLUTION OF ONTOGENY IN VOLVOX
ARCH PROTISTENKD 141 (3): 171-178 APR 1992
Abstract:
The green flagellates of the genus Volvox can be conditionally
subdivided into two groups according to the size of gonidia (asexual
reproductive cells) at the onset of cleavage. In Volvox carteri and
several other species the gonidium undergoes an extended period of
hypertrophied growth, after which a series of rapid fissions occurs. Embryonic
cells do not grow during the intervals between consecutive divisions. In
representatives of the second group (e.g., V. aureus) the period of gonidial
enlargement is comparatively nondurable; thus the cleavage begins when the
gonidium is relatively small, and each division is followed by a period of
cellular growth.
In this paper the evolutionary relationships between two types of asexual life cycle in Volvox are analysed on the basis of literary and our own data. It is supposed that the V. aureus type of development with slow divisions of small gonidia is more advanced in the evolutionary respect than the V. carteri type of development with rapid divisions of large gonidia.
Experimental analysis of the role of light and dark for embryonic cleavage progression in V. aureus, V. carteri f. nagariensis and V. tertius as well as the experiments with several metabolic inhibitors (aminopterin, actinomycin D, cycloheximide and streptomycin) have enabled us to elucidate cellular mechanisms of the evolution of ontogenesis in Volvox.
MENGELE R, SUMPER M
GULOSE AS A
CONSTITUENT OF A GLYCOPROTEIN
FEBS LETT 298 (1): 14-16
Abstract:
The aldohexose gulose was identified as a constituent of a hydroxyproline-rich
glycopeptide derived from the glycoprotein SSG 185. This glycoprotein is part
of the extracellular matrix of the green alga Volvox carteri. The gulose
residue occupies a terminal position in the corresponding saccharide.
ALHASANI H, JAENICKE L
CHARACTERIZATION
OF THE SEX-INDUCER GLYCOPROTEIN OF VOLVOX-CARTERI
F WEISMANNIA
SEX PLANT REPROD 5 (1): 8-12 JAN 1992
Abstract:
Sexual inducer pheromones from Volvox carteri f. weismannia, strains
65-30(12) and 1B were purified and characterized as glycoproteins with apparent
molecular weights of 27 kDa and 28.5 kDa, respectively. This subspecies yielded
20-40 times more pheromone based on weight per spheroid than Volvox carteri
f. nagariensis, but its specific activity (threshold dilution) is four to five
orders of magnitude less (10(-12) to 10(-13) M). Gas-chromatographic sugar
analysis revealed quantitative differences in the composition of the O- and
N-glucans compared with the V. carteri f. nagariensis inducer. The V. carteri
f. weismannia pheromones showed antigenic cross-reaction with an antiserum
directed against chemically deglycosylated inducer from V. carteri f.
nagariensis. However, there is only unilateral biological cross-induction. The
V. carteri f. nagariensis inducer is strictly competent for its own gonidia
only; the inducers from V. carteri f. weismannia also cross-induce V. carteri
f. nagariensis. This pattern of cross-induction suggests the existence of related
pheromone receptors but with different ligand specificities.
LARSON A, KIRK MM, KIRK DL
MOLECULAR
PHYLOGENY OF THE VOLVOCINE FLAGELLATES
MOL BIOL EVOL 9 (1): 85-105 JAN 1992
Abstract:
Phylogenetic studies of approximately 2,000 bases of sequence from the large
and small nuclear-encoded ribosomal RNAs are used to investigate the origins of
the genus Volvox. The colonial and multicellular genera currently placed
in the family Volvocaceae form a monophyletic group that is significantly
closer phylogenetically to Chlamydomonas reinhardtii than it is to the other
unicellular green flagellates that were tested, including Chlamydomonas
eugametos, Chlorella pyrenoidosa, and Haematococcus lacustris. Statistical
analysis of 251 phylogenetically informative nucleotide positions rejects the
"volvocine lineage" hypothesis, which postulates a monophyletic
evolutionary progression from unicellular organisms (such as Chlamydomonas),
through colonial organisms (e.g., Gonium, Pandorina, Eudorina, and Pleodorina)
demonstrating increasing size, cell number, and tendency toward cellular
differentiation, to multicellular organisms having fully differentiated somatic
and reproductive cells (in the genus Volvox). The genus Volvox
appears not to be monophyletic. Volvox capensis falls outside a lineage
containing other representatives of Volvox(V. aureus, V. carteri, and V.
obversus), and both of these Volvox lineages are more closely related to
certain colonial genera than they are to each other. This implies either a
diphyletic origin of Volvox from different colonial volvocacean
ancestors, a phylogenetic derivation of some of the colonial genera from a
multicellular (i.e., Volvox) ancestor, or both. Considered together with
previously published observations, these results suggest that the different
levels of organizational and developmental complexity found in the Volvocaceae
represent alternative stable states, among which evolutionary transitions have
occurred several times during the phylogenetic history of this group.
SCHMITT R, FABRY S, KIRK DL
IN SEARCH OF
MOLECULAR-ORIGINS OF CELLULAR-DIFFERENTIATION IN VOLVOX AND ITS RELATIVES
INT REV CYTOL 139: 189-265 1992
MENGELE R, SUMPER M
GULOSE AS A
CONSTITUENT OF A GLYCOPROTEIN
FEBS LETT 298 (1): 14-16
1991
KOUFOPANOU V,
DEVELOPMENTAL
MUTANTS OF VOLVOX - DOES MUTATION
RECREATE THE PATTERNS OF PHYLOGENETIC DIVERSITY
EVOLUTION 45 (8): 1806-1822 DEC 1991
Abstract:
The nature of the variation which is created by mutation can show how the
direction of evolution is constrained by internal biases arising from development
and pre-existing design. We have attempted to quantify these biases by
measuring eight life history characters in developmental mutants of Volvox
carteri. Most of the mutants in our sample were inferior to the wild type, but
deviated by less than tenfold from the wild-type mean. Characters differed in
mutability, suggesting different levels of canalisation. Most correlations
between life history characters among strains were positive, but there was a
significant negative correlation between the size and the number of
reproductive cells, suggesting an upper limit to the total quantity of germ
produced by individuals. The most extreme phenotypes in our sample were very
vigorous, showing that not all mutations of large effect are unconditionally
deleterious. We investigated the effect of developmental constraints on the
course of evolution by comparing the variance and covariance patterns among
mutant strains with those among species in the family Volvocaceae. A close
correspondence between patterns at these two levels would suggest that
pre-existing design has a strong influence on evolution, while little or no
correspondence shows the action of selection. The variance generated by
mutation was equal to that generated by speciation in the family Volvocaceae,
the genus Volvox, or the section Merillosphaera, depending on the
character considered. We found that mutation changes the volume of somatic
tissue independently of the quantity of germ tissue, so that the interspecific
correlation between soma and germ can be attributed to selection. The negative
correlation between size and number of germ cells among mutants of V. carteri
is also seen among the larger members of the family (Volvox spp.), but
not among the smaller members, suggesting a powerful design constraint that may
be responsible for the absence of larger forms in the entire group.
HAAS E, SUMPER M
THE SEXUAL
INDUCER OF VOLVOX-CARTERI - ITS
LARGE-SCALE PRODUCTION AND SECRETION BY SACCHAROMYCES-CEREVISIAE
FEBS LETT 294 (3): 282-284 DEC 9 1991
Abstract:
The DNA sequence coding for the sexual inducer glycoprotein of Volvox
carteri and its N-terminal signal peptide was placed under the control of the
repressible acid phosphatase promoter of the yeast Saccharomyces cerevisiae in
a yeast-E. coli shuttle vector. Yeast transformed by this construct synthesized
and secreted into the culture medium biologically active inducer in amounts two
to three orders of magnitude higher than observed in the Volvox system.
JAENICKE L, VANLEYEN K, SIEGMUND HU
DOLICHYL
PHOSPHATE-DEPENDENT GLYCOSYLTRANSFERASES UTILIZE TRUNCATED COFACTORS
BIOL CHEM H-S 372 (11): 1021-1026 NOV 1991
Abstract:
Synthetic truncated dolichyl phosphates of chain lengths from four to thirteen
isoprene units (Jaenicke L. and Siegmund H.-U., Chem. Phys. Lipids 51 (1989) 159-170)
were assayed for their cofactor activity in the enzymatic transfer of hexoses
and hexosamines. The enzymes were microsomal preparations from the green alga Volvox
carteri, baker's yeast, and mammalian liver cells. Under saturating conditions,
the acceptor activities of the truncated dolichyl phosphates increased from
zero to full strength as compared to the mixture of long-chain dolichyl
phosphates from natural sources with growing chain length from five to nine
isoprene units. K(m) determinations confirmed the results. Of the geometric
isomers of dolichyl 7-phosphate (35 carbon atoms), the 14-trans compound has
unchanged acceptor activity; all-trans dolichyl 7-phosphate, however, was
almost inactive. The data suggest that hydrophobicity may be an important, but
not the only criterion for the binding of the isoprene moiety to the active
sites of the transferase enzyme(s) and that the geometry of more than only one
double bond in the dolichols is recognized.
KIRK DL, KAUFMAN MR, KEELING RM, et al.
GENETIC AND
CYTOLOGICAL CONTROL OF THE ASYMMETRIC DIVISIONS THAT PATTERN THE VOLVOX EMBRYO
DEVELOPMENT : 67-82 Suppl. 1 1991
Abstract:
The highly regular pattern in which approximately 2000 small somatic cells and
16 large reproductive cells (or 'gonidia') are arranged in a typical asexual
adult of Volvox carteri can be traced back to a stereotyped program of
embryonic cleavage divisions. After five symmetrical divisions have produced 32
cells of equal size, the anterior 16 cells cleave asymmetrically, to produce
one small somatic cell initial and one larger gonidial initial each. The
gonidial initials then cease dividing before the somatic cell initials do. The
significance of the visibly asymmetric divisions is underscored by genetic and
experimental evidence that differences in size - rather than differences in
cytoplasmic quality - are causally important in activating the programs that
cause small cells to become mortal somatic cells and large cells to
differentiate as reproductive cells. A number of loci, including at least five
mul ('multiple gonidia') loci, appear to be responsible for determining where
and when asymmetric divisions will occur, since mutations at these loci result
in modified temporal and/or spatial patterns of asymmetric division in one or
more portions of the life cycle. But the capacity to divide asymmetrically at
all appears to require a function encoded by the gls (gonidialess) locus, since
gls mutants fail to execute any asymmetric divisions. Second-site suppressors
of gls that have been identified may encode other functions required for
asymmetric division. Cytological and immunocytochemical studies of dividing
embryos are being undertaken in an attempt to elucidate the mechanisms by which
cell-division planes are established - and shifted - under the influence of
such pattern-specifying genes. Studies to date clearly indicate a central role
for the basal body apparatus, and particularly its microtubular rootlets, in
establishing the orientation of both the mitotic spindle and the cleavage
furrow; but it remains to be determined how behavior of the division apparatus
becomes modified during asymmetric division.
WAYNE R, KADOTA A, WATANABE M, et al.
PHOTOMOVEMENT
IN DUNALIELLA-SALINA - FLUENCE RATE-RESPONSE CURVES AND ACTION SPECTRA
PLANTA 184 (4): 515-524 1991
Abstract:
We determined the action spectra of the photophobic responses as well as the
phototactic response in Dunaliella salina (Volvocales) using both single cells
and populations. The action spectra of the photophobic responses have maximum
at 510 nm, the spectrum for phototaxis has a maximum at 450-460 nm. These
action spectra are not compatible with the hypothesis that flavoproteins are
the photoreceptor pigments, and we suggest that carotenoproteins or rhodopsins
act as the photoreceptor pigments. We also conclude that the phototactic
response in Dunaliella is an elementary response, quite independent of the
step-up and step-down photophobic responses. We also determined the action
spectra of the photoaccumulation response in populations of cells adapted to
two different salt conditions. Both action spectra have a peak a 490 nm. The
photoaccumulation response may be a complex response composed of the
phototactic and photophobic responses. Blue or blue-green light does not elicit
a photokinetic response in Dunaliella.
TAM LW, KIRK DL
THE PROGRAM
FOR CELLULAR-DIFFERENTIATION IN VOLVOX-CARTERI
AS REVEALED BY MOLECULAR ANALYSIS OF DEVELOPMENT IN A GONIDIALESS SOMATIC
REGENERATOR MUTANT
DEVELOPMENT 112 (2): 571-580 JUN 1991
Abstract:
Development of a 'gonidialess'/'somatic regenerator' double mutant of Volvox
carteri was analyzed with a number of cell-type-specific cDNA probes that had
been identified in a previous study. Whereas in wild-type strains somatic cells
and gonidia (asexual reproductive cells) constitute two distinct cell lineages,
in this mutant all cells first differentiate as somatic cells and then
redifferentiate as gonidia. During the initial period of somatic differentiation,
we found that both gonidial and 'early' somatic transcripts were accumulated in
the mutant, consistent with the idea that it is the regA gene product (which is
defective in this mutant) that normally acts to suppress gonidial gene
expression in somatic cells. Later in development, levels of early somatic
transcripts fell abruptly, levels of the late somatic transcripts remained
extremely low, and levels of gonidial transcripts rose as the cells
redifferentiated. Thus it appears that in the mutant cells the gonidial program
of development takes over and somatic differentiation is aborted before the
stage at which late somatic genes are normally activated. These results provide
molecular genetic support for a model which postulates that three types of
genes (including the two that are defective in the strain studied here) are
crucial for converting the sequential program of differentiation seen in more
primitive volvocalean algae to the dichotomous program of germ-soma
differentiation that occurs in wild-type V. carteri.
ROSATI G, VERNI F
SEXUAL
RECOGNITION IN PROTOZOA - CHEMICAL SIGNALS AND TRANSDUCTION MECHANISMS
ZOOL SCI 8 (3): 415-429 JUN 1991
TAM LW, STAMER KA, KIRK DL
EARLY AND
LATE GENE-EXPRESSION PROGRAMS IN DEVELOPING SOMATIC-CELLS OF VOLVOX-CARTERI
DEV BIOL 145 (1): 67-76 MAY 1991
RANSICK A
REPRODUCTIVE
CELL SPECIFICATION DURING VOLVOX-OBVERSUS
DEVELOPMENT
DEV BIOL 143 (1): 185-198 JAN 1991
1990
BUCHHEIM MA, TURMEL M, ZIMMER EA, et al.
PHYLOGENY OF
CHLAMYDOMONAS (CHLOROPHYTA) BASED ON CLADISTIC-ANALYSIS OF NUCLEAR 18S
RIBOSOMAL-RNA SEQUENCE DATA
J PHYCOL 26 (4): 689-699 DEC 1990
Abstract:
The genus Chlamydomonas Ehrenberg may contain as many as 450 described species.
Morphological, physiological and molecular data show that variation among some
Chlamydomonas species can be great, leading to speculation that multiple,
generic-level lineages exist within this genus. The most recent systematic
studies of Chlamydomonas have led to proposals of nine distinct morphological
and 15 distinct sporangial autolysin groups. Partial sequences from the nuclear
small subunit rNAs from 14 Chlamydomonas species representing 12 autolysin and
four morphological groups, and from three flagellates thought to be related to
Chlamydomonas were determined in a phylogenetic study of relationships among
these algae. Sequence comparisons among some Chlamydomonas species revealed
differences comparable to the sequence divergence between soybeans and cycads.
Cladistic analysis of the sequence data suggests that multiple lineages exist
among species of Chlamydomonas. Some of these lineages represent alliances of
both Chlamydomonas and non-Chlamydomonas taxa; thus, the current taxonomy does
not reflect natural, or monophyletic, groups. Collectively, these lineages may
represent distinct families or even orders.
CRESNAR B, MAGES W, MULLER K, et al.
STRUCTURE AND
EXPRESSION OF A SINGLE ACTIN GENE IN VOLVOX-CARTERI
CURR GENET 18 (4): 337-346 NOV 1990
MULLER K, LINDAUER A, BRUDERLEIN M, et al.
ORGANIZATION
AND TRANSCRIPTION OF VOLVOX
HISTONE-ENCODING GENES - SIMILARITIES BETWEEN ALGAL AND ANIMAL GENES
GENE 93 (2): 167-175
BALSHUSEMANN D, JAENICKE L
THE
OLIGOSACCHARIDES OF THE GLYCOPROTEIN PHEROMONE OF VOLVOX-CARTERI F NAGARIENSIS IYENGAR (CHLOROPHYCEAE)
EUR J BIOCHEM 192 (1): 231-237
PATTERNS OF
ORGANELLAR AND NUCLEAR INHERITANCE AMONG PROGENY OF 2 GEOGRAPHICALLY ISOLATED
STRAINS OF VOLVOX-CARTERI
CURR GENET 18 (2): 141-153 AUG 1990
BALSHUSEMANN D, JAENICKE L
TIME AND MODE
OF SYNTHESIS OF THE SEXUAL INDUCER GLYCOPROTEIN OF VOLVOX-CARTERI
FEBS LETT 264 (1): 56-58
WAFFENSCHMIDT S, KNITTLER M, JAENICKE L
CHARACTERIZATION
OF A SPERM LYSIN OF VOLVOX-CARTERI
SEX PLANT REPROD 3 (1): 1-6 FEB 1990
1989
ERTL H, MENGELE R, WENZL S, et al.
THE
EXTRACELLULAR-MATRIX OF VOLVOX-CARTERI
- MOLECULAR-STRUCTURE OF THE CELLULAR COMPARTMENT
J CELL BIOL 109 (6): 3493-3501 Part 2 DEC 1989
BALSHUSEMANN D, GILLES R, JAENICKE L
THE
BIOCHEMISTRY OF THE SEX INDUCER OF VOLVOX-CARTERI
BIOL CHEM H-S 370 (9): 873-874 SEP 1989
FELDWISCH O, ERK H, JAENICKE L
CYCLIC-AMP
BINDING-PROTEIN AND PHOSPHODIESTERASES IN VOLVOX-CARTERI
BIOL CHEM H-S 370 (9): 895-895 SEP 1989
FELDWISCH O, ERK H, JAENICKE L
CYCLIC-AMP
BINDING-PROTEIN AND PHOSPHODIESTERASES IN VOLVOX-CARTERI
BIOL CHEM H-S 370 (9): 895-895 SEP 1989
HOLST O, CHRISTOFFEL V, FRUND R, et al.
A
PHOSPHODIESTER BRIDGE BETWEEN 2 ARABINOSE RESIDUES AS A STRUCTURAL ELEMENT OF
AN EXTRACELLULAR GLYCOPROTEIN OF VOLVOX-CARTERI
EUR J BIOCHEM 181 (2): 345-350
1988
KASKA DD, MYLLYLA R, GUNZLER V, et al.
PROLYL
4-HYDROXYLASE FROM VOLVOX-CARTERI
- A LOW-MR ENZYME ANTIGENICALLY RELATED TO THE ALPHA-SUBUNIT OF THE VERTEBRATE
ENZYME
BIOCHEM J 256 (1): 257-263
HARPER JF, MAGES W
ORGANIZATION
AND STRUCTURE OF VOLVOX
BETA-TUBULIN GENES
MOL GEN GENET 213 (2-3): 315-324 AUG 1988
MAGES W, SALBAUM JM, HARPER JF, et al.
ORGANIZATION
AND STRUCTURE OF VOLVOX
ALPHA-TUBULIN GENES
MOL GEN GENET 213 (2-3): 449-458 AUG 1988
GOODENOUGH UW, HEUSER JE
MOLECULAR-ORGANIZATION
OF CELL-WALL CRYSTALS FROM CHLAMYDOMONAS-REINHARDTII AND VOLVOX-CARTERI
J CELL SCI 90: 717-733 Part
MAGES HW, TSCHOCHNER H, SUMPER M
THE SEXUAL
INDUCER OF VOLVOX-CARTERI
PRIMARY STRUCTURE DEDUCED FROM CDNA SEQUENCE
FEBS LETT 234 (2): 407-410
NOZAKI H
MORPHOLOGY,
SEXUAL REPRODUCTION AND TAXONOMY OF VOLVOX-CARTERI
F KAWASAKIENSIS F NOV (CHLOROPHYTA) FROM JAPAN
PHYCOLOGIA 27 (2): 209-220 JUN 1988
MULLER K, SCHMITT R
HISTONE GENES
OF VOLVOX-CARTERI - DNA-SEQUENCE
AND ORGANIZATION OF 2 H3-H4 GENE LOCI
NUCLEIC ACIDS RES 16 (9): 4121-4136
KIRK DL
THE ONTOGENY
AND PHYLOGENY OF CELLULAR-DIFFERENTIATION IN VOLVOX
TRENDS GENET 4 (2): 32-36 FEB 1988
1987
ADAIR WS, STEINMETZ SA, MATTSON DM, et al.
NUCLEATED
ASSEMBLY OF CHLAMYDOMONAS AND VOLVOX
CELL-WALLS
J CELL BIOL 105 (5): 2373-2382 NOV 1987
MULLER K, RAUSCH H, SCHMITT R
MOLECULAR
EVOLUTION OF VOLVOX CARTERI
PROBED WITH HISTONE AND RDNA GENES
BIOL CHEM H-S 368 (9): 1084-1084 SEP 1987
GUNTHER R, BAUSE E, JAENICKE L
UDP-L-ARABINOSE-HYDROXYPROLINE-O-GLYCOSYLTRANSFERASES IN VOLVOX-CARTERI
FEBS LETT 221 (2):
293-298 SEP 14 1987
HARPER JF, HUSON KS, KIRK DL
USE OF
REPETITIVE SEQUENCES TO IDENTIFY DNA POLYMORPHISMS LINKED TO REGA, A
DEVELOPMENTALLY IMPORTANT LOCUS IN VOLVOX
GENE DEV 1 (6): 573-584 AUG 1987
TSCHOCHNER H, LOTTSPEICH F, SUMPER M
THE SEXUAL
INDUCER OF VOLVOX-CARTERI -
PURIFICATION, CHEMICAL CHARACTERIZATION AND IDENTIFICATION OF ITS GENE
EMBO J 6 (8): 2203-2207 AUG 1987
KIRK DL, BARAN GJ, HARPER JF, et al.
STAGE-SPECIFIC
HYPERMUTABILITY OF THE REGA LOCUS OF VOLVOX,
A GENE REGULATING THE GERM SOMA DICHOTOMY
CELL 48 (1): 11-24
1986
SCHLIPFENBACHER R, WENZL S, LOTTSPEICH F, et al.
AN EXTREMELY
HYDROXYPROLINE-RICH GLYCOPROTEIN IS EXPRESSED IN INVERTING VOLVOX EMBRYOS
FEBS LETT 209 (1): 57-62 DEC 1 1986
KIRK DL, KIRK MM
HEAT-SHOCK ELICITS
PRODUCTION OF SEXUAL INDUCER IN VOLVOX
SCIENCE 231 (4733): 51-54
COGGIN SJ, KOCHERT G
FLAGELLAR
DEVELOPMENT AND REGENERATION IN VOLVOX-CARTERI
(CHLOROPHYTA)
J PHYCOL 22 (3): 370-381 SEP 1986
WENZL S, SUMPER M
A NOVEL
GLYCOSPHINGOLIPID THAT MAY PARTICIPATE IN EMBRYO INVERSION IN VOLVOX CARTERI
CELL 46 (4): 633-639
SOMMER U, GLIWICZ ZM
LONG-RANGE
VERTICAL MIGRATION OF VOLVOX IN
TROPICAL LAKE CAHORA BASSA (MOZAMBIQUE)
LIMNOL OCEANOGR 31 (3): 650-653 MAY 1986
KIRK DL, HARPER JF
GENETIC,
BIOCHEMICAL, AND MOLECULAR APPROACHES TO VOLVOX DEVELOPMENT AND EVOLUTION
INT REV CYTOL 99: 217-293 1986
WENZL S, SUMPER M
EARLY EVENT
OF SEXUAL INDUCTION IN VOLVOX -
CHEMICAL MODIFICATION OF THE EXTRACELLULAR-MATRIX
DEV BIOL 115 (1): 119-128 MAY 1986
BARAN GJ, HUSKEY RJ
DEVELOPMENTAL-CHANGES
IN THE SENSITIVITY OF VOLVOX TO
ULTRAVIOLET-LIGHT
DEV GENET 6 (4): 269-280 1986
KIRK DL, KIRK MM
GENETIC AND
ENVIRONMENTAL-REGULATION OF DETERMINATION AND DIFFERENTIATION IN VOLVOX
J CELL BIOCHEM : 37-37 Suppl. 10D 1986
SCHMITT R, MULLER K, RAUSCH H, et al.
HOUSEKEEPING
GENES AND THEIR EXPRESSION IN THE GENERATION CYCLE OF VOLVOX-CARTERI
J CELL BIOCHEM : 43-43 Suppl. 10D 1986
KIRK DL, BIRCHEM R, KING N
THE
EXTRACELLULAR-MATRIX OF VOLVOX -
A COMPARATIVE-STUDY AND PROPOSED SYSTEM OF NOMENCLATURE
J CELL SCI 80: 207-231 FEB 1986
1985
JAENICKE L, GILLES R
GERM-CELL
DIFFERENTIATION IN VOLVOX-CARTERI
DIFFERENTIATION 29 (3): 199-206 1985
GILLES R, MOKA R, JAENICKE L
THE
EXTRACELLULAR-MATRIX PLAYS A FUNCTIONAL-ROLE IN SEXUAL-DIFFERENTIATION OF VOLVOX CARTERI
BIOL CHEM H-S 366 (9): 793-794 1985
KIRK MM, KIRK DL
TRANSLATIONAL
REGULATION OF PROTEIN-SYNTHESIS, IN RESPONSE TO LIGHT, AT A CRITICAL STAGE OF VOLVOX DEVELOPMENT
CELL 41 (2): 419-428 1985
GILLES R, MOKA R, GILLES C, et al.
CYCLIC-AMP AS
AN INTRASPHEROIDAL DIFFERENTIATION SIGNAL IN VOLVOX-CARTERI
FEBS LETT 184 (2): 309-312 1985
KOPAN R, KURN N, OVADIA M
SYNTHESIS AND
POSSIBLE ROLE OF PROTEOGLYCANS DURING VOLVOX
DEVELOPMENT
CELL DIFFER DEV 16 (2): 119-132 1985
1984
WEISSHAAR B, GILLES R, MOKA R, et al.
A
HIGH-FREQUENCY MUTATION STARTS SEXUAL REPRODUCTION IN VOLVOX-CARTERI
Z NATURFORSCH C 39 (11-1): 1159-1162 1984
HOFFMAN JL
MONOCLONAL-ANTIBODIES
TO SURFACE COMPONENTS OF VOLVOX
J CELL BIOL 99 (4): A243-A243 1984
GILLES R, JAENICKE L
EXTRACELLULAR
PHOSPHOPROTEINS ARE INVOLVED IN SEXUAL-DIFFERENTIATION OF VOLVOX-CARTERI
H-S Z PHYSIOL CHEM 365 (9): 990-990 1984
GILLES R, GILLES C, JAENICKE L
PHEROMONE-BINDING
AND MATRIX-MEDIATED EVENTS IN SEXUAL INDUCTION OF VOLVOX-CARTERI
Z NATURFORSCH C 39 (6): 584-592 1984
WENZL S, THYM D, SUMPER M
DEVELOPMENT-DEPENDENT
MODIFICATION OF THE EXTRACELLULAR-MATRIX BY A SULFATED GLYCOPROTEIN IN VOLVOX-CARTERI
EMBO J 3 (4): 739-744 1984
HOOPS HJ
SOMATIC-CELL
FLAGELLAR APPARATUSES IN 2 SPECIES OF VOLVOX
(CHLOROPHYCEAE)
J PHYCOL 20 (1): 20-27 1984
MULLER T, BAUSE E, JAENICKE L
EVIDENCE FOR
AN INCOMPLETE DOLICHYL-PHOSPHATE PATHWAY OF LIPOGLYCAN FORMATION IN VOLVOX-CARTERI F NAGARIENSIS
EUR J BIOCHEM 138 (1): 153-159 1984
1983
REYNOLDS CS PENTECOST A
THE
DISTRIBUTION OF DAUGHTER COLONIES AND CELL NUMBERS IN A NATURAL-POPULATION OF VOLVOX-AUREUS EHRENB
ANN BOT-LONDON 52 (5): 769-776 1983
GROWTH-RATE
RESPONSES OF VOLVOX-AUREUS
EHRENB (CHLOROPHYTA, VOLVOCALES) TO VARIABILITY IN THE PHYSICAL-ENVIRONMENT
BRIT PHYCOL J 18 (4): 433-442 1983
GILLES R, GILLES C, JAENICKE L
SEXUAL-DIFFERENTIATION
OF THE GREEN-ALGA VOLVOX-CARTERI
- INVOLVEMENT OF EXTRACELLULAR PHOSPHORYLATED PROTEINS
NATURWISSENSCHAFTEN 70 (11): 571-572 1983
HOFFMAN JL
EFFECTS OF
MONENSIN TREATMENT ON SEXUAL DEVELOPMENT IN VOLVOX
J CELL BIOL 97 (5): A63-A63 1983
MATTSON DM, GREEN KJ
BASAL BODY
ABNORMALITIES IN A MORPHOGENETIC MUTANT OF VOLVOX
J CELL BIOL 97 (5): A206-A206 1983
HARPER JF, KIRK DL
LINKAGE
ANALYSIS OF VOLVOX MORPHOGENETIC
MUTANTS, USING A MAP BASED ON RESTRICTION POLYMORPHISMS
J CELL BIOL 97 (5): A327-A327 1983
VASILETS V, COTTRELL SF
AGE-DEPENDENT
ALTERATIONS IN THE SOMATIC-CELLS OF VOLVOX-CARTERI
J CELL BIOL 97 (5): A345-A345 1983
GANF GG, SHIEL RJ, MERRICK CJ
PARASITISM -
THE POSSIBLE CAUSE OF THE COLLAPSE OF A VOLVOX
POPULATION IN MOUNT BOLD RESERVOIR, SOUTH-AUSTRALIA
AUST J MAR FRESH RES 34 (3): 489-494 1983
WEINHEIMER T
CELLULAR-DEVELOPMENT
IN THE GREEN-ALGA VOLVOX-CARTERI
CYTOBIOS 36 (143-): 161-173 1983
KIRK DL, KIRK MM
PROTEIN
SYNTHETIC PATTERNS DURING THE ASEXUAL LIFE-CYCLE OF VOLVOX-CARTERI
DEV BIOL 96 (2): 493-506 1983
BAUSE E, MULLER T, JAENICKE L
SYNTHESIS AND
CHARACTERIZATION OF LIPID-LINKED MANNOSYL OLIGOSACCHARIDES IN VOLVOX-CARTERI F-NAGARIENSIS
ARCH BIOCHEM BIOPHYS 220 (1): 200-207 1983
1982
COLEMAN AW, MAGUIRE MJ
A
MICROSPECTROFLUOROMETRIC ANALYSIS OF NUCLEAR AND CHLOROPLAST DNA IN VOLVOX
DEV BIOL 94 (2): 441-450 1982
GILLES R, JAENICKE L
DIFFERENTIATION
IN VOLVOX-CARTERI - STUDY OF
PATTERN VARIATION OF REPRODUCTIVE CELLS
Z NATURFORSCH C 37 (10): 1023-1030 1982
BARAN GJ, HUSKEY RJ
GENE-EXPRESSION
DURING RE-DIFFERENTIATION OF SOMATIC-CELLS IN VOLVOX
J CELL BIOL 95 (2): A48-A48 1982
PANNAMAN L, ELMANN E, BLAMIRE J, et al.
AGE-DEPENDENT
RELEASE OF DAUGHTER SPHEROIDS IN VOLVOX
CARTERI-F-NAGARIENSIS
J CELL BIOL 95 (2): A117-A117 1982
MATTSON DM, BRYANT JL, GREEN KJ, et al.
GENETIC
LESIONS OF CYTOSKELETON-MEDIATED MORPHOGENESIS IN VOLVOX
J CELL BIOL 95 (2): A353-A353 1982
HARPER JF
TUBULIN GENES
OF VOLVOX-CARTERI
J CELL BIOL 95 (2): A353-A353 1982
MULLER T, BAUSE E, JAENICKE L
FORMATION OF LIPID-LINKED
MANNOSYL OLIGOSACCHARIDES IN VOLVOX-CARTERI
H-S Z PHYSIOL CHEM 363 (9): 1035-1035 1982
GREEN KJ, KIRK DL
A REVISION OF
THE CELL LINEAGES RECENTLY REPORTED FOR VOLVOX-CARTERI
EMBRYOS
J CELL BIOL 94 (3): 741-742 1982
POMMERVILLE J, KOCHERT G
EFFECTS OF
SENESCENCE ON SOMATIC-CELL PHYSIOLOGY IN THE GREEN-ALGA VOLVOX-CARTERI
EXP CELL RES 140 (1): 39-45 1982
KURN N, DUKSIN D
EXTRACELLULAR-MATRIX
GLYCOPROTEINS OF VOLVOX-CARTERI
KURN N
INHIBITION OF
PHOSPHATE-UPTAKE BY FLUPHENAZINE, A CALMODULIN INHIBITOR - ANALYSIS OF VOLVOX WILD-TYPE AND
FLUPHENAZINE-RESISTANT MUTANT STRAINS
FEBS LETT 144 (1): 68-72 1982
KURN N, DUKSIN D
EFFECTS OF
TUNICAMYCIN ON PROTEIN GLYCOSYLATION AND DEVELOPMENT IN VOLVOX-CARTERI
ROUX ARCH DEV BIOL 191 (3): 169-175 1982
WENZL S, SUMPER M
THE
OCCURRENCE OF DIFFERENT SULFATED CELL-SURFACE GLYCOPROTEINS CORRELATES WITH DEFINED
DEVELOPMENTAL EVENTS IN VOLVOX
FEBS LETT 143 (2): 311-315 1982
WILLADSEN P, SUMPER M
SULFATION OF
A CELL-SURFACE GLYCOPROTEIN FROM VOLVOX-CARTERI
- EVIDENCE FOR A MEMBRANE-BOUND SULFOKINASE WORKING WITH PAPS
FEBS LETT 139 (1): 113-116 1982
J CELL BIOL 91 (2): A21-A21 1981 JAENICKE L
VOLVOX BIOCHEMISTRY COMES OF AGE
TRENDS BIOCHEM SCI 7 (2): 61-64 1982
1981
POMMERVILLE J, KOCHERT G
SOMATIC-CELL
SENESCENCE IN THE GREEN-ALGA VOLVOX
J CELL BIOL 91 (2): A17-A17 1981
HOFFMAN JL
SPECIFIC
POLYPEPTIDE-SYNTHESIS DURING SEXUAL DEVELOPMENT IN VOLVOX
J CELL BIOL 91 (2): A21-A21 1981
BARAN GJ, HUSKEY RJ
MOLECULAR
ANALYSIS OF CYTODIFFERENTIATION IN VOLVOX
CARTERI
J CELL BIOL 91 (2): A33-A33 1981
TEMPLEMAN MN, MCGOWAN RE, BLAMIRE J, et al.
CHARACTERIZATION
AND COMPARISON OF THE EXTRACELLULAR-MATRIX IN HETEROGENOUS POPULATIONS OF 2
STRAINS OF VOLVOX-CARTERI
J CELL BIOL 91 (2): A159-A159 1981
GREEN KJ, KIRK DL
THE MECHANISM
OF CYTOKINESIS DURING CLEAVAGE IN VOLVOX
J CELL BIOL 91 (2): A166-A166 1981
MCCRACKEN MD, BARCELLONA WJ
ULTRASTRUCTURE
OF SHEATH SYNTHESIS IN VOLVOX-ROUSSELETII
CYTOBIOS 32 (127-): 179-187 1981
KURN N, SELA BA
ALTERED
CALMODULIN ACTIVITY IN FLUPHENAZINE-RESISTANT MUTANT STRAINS - PLEIOTROPIC
EFFECT ON DEVELOPMENT AND CELLULAR-ORGANIZATION IN VOLVOX-CARTERI
EUR J BIOCHEM 121 (1): 53-57 1981
MILLER CE, STARR RC
THE CONTROL
OF SEXUAL MORPHOGENESIS IN VOLVOX-CAPENSIS
BER DEUT BOT GES 94 (3): 357-372 1981
JAENICKE L, WAFFENSCHMIDT S
LIBERATION OF
REPRODUCTIVE UNITS IN VOLVOX AND
CHLAMYDOMONAS - PROTEOLYTIC PROCESSES
BER DEUT BOT GES 94 (3): 375-386 1981
SENFT WH, HUNCHBERGER RA, ROBERTS KE
TEMPERATURE-DEPENDENCE
OF GROWTH AND PHOSPHORUS UPTAKE IN 2 SPECIES OF VOLVOX (VOLVOCALES, CHLOROPHYTA)
J PHYCOL 17 (4): 323-329 1981
GREEN KJ, KIRK DL
CLEAVAGE
PATTERNS, CELL LINEAGES, AND DEVELOPMENT OF A CYTOPLASMIC BRIDGE SYSTEM IN VOLVOX EMBRYOS
J CELL BIOL 91 (3): 743-755 1981
GREEN KJ, VIAMONTES GI, KIRK DL
MECHANISM OF
FORMATION, ULTRASTRUCTURE, AND FUNCTION OF THE CYTOPLASMIC BRIDGE SYSTEM DURING
MORPHOGENESIS IN VOLVOX
J CELL BIOL 91 (3): 756-769 1981
KURN N
ALTERED
DEVELOPMENT OF THE MULTICELLULAR ALGA VOLVOX-CARTERI
CAUSED BY LECTIN BINDING
CELL BIOL INT REP 5 (9): 867-875 1981
KURN N, SELA B
ALTERED
CALMODULIN ACTIVITY AND ABERRANT DEVELOPMENT IN FLUPHENAZINE RESISTANT VOLVOX MUTANT STRAINS
POMMERVILLE JC, KOCHERT GD
CHANGES IN
SOMATIC-CELL STRUCTURE DURING SENESCENCE OF VOLVOX CARTERI
EUR J CELL BIOL 24 (2): 236-243 1981
WENZL S, SUMPER M
SULFATION OF
A CELL-SURFACE GLYCOPROTEIN CORRELATES WITH THE DEVELOPMENTAL PROGRAM DURING
EMBRYOGENESIS OF VOLVOX-CARTERI
P NATL ACAD SCI-BIOL 78 (6): 3716-3720 1981
MULLER T, BAUSE E, JAENICKE L
GLYCOLIPID
FORMATION IN VOLVOX-CARTERI-F-NAGARIENSIS
- EFFECTS OF TUNICAMYCIN AND SHOWDOMYCIN
FEBS LETT 128 (2): 208-212 1981
INVERSION IN VOLVOX-TERTIUS - THE EFFECTS OF CON-A
J CELL SCI 48 (APR): 355-366 1981
GILLES R, BITTNER C, JAENICKE L
SITE AND TIME
OF FORMATION OF THE SEX-INDUCING GLYCOPROTEIN IN VOLVOX-CARTERI
FEBS LETT 124 (1): 57-60 1981
1980
ZEIKUS JA, DARDEN WH, BROOKS D
SEXUAL
SPHEROID FORMATION IN VOLVOX-CARTERI
F NAGARIENSIS LYENGAR INDUCED BY PHENOLIC EXTRACTS
MICROBIOS 28 (113-): 173-184 1980
A METHOD FOR
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MICROBIOS 28 (113-): 185-201 1980
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CYTOBIOS 29 (114): 115-128 1980
DARDEN WH
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MICROBIOS 28 (111): 27-39 1980
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DEV BIOL 80 (2): 419-435 1980
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COTTRELL SF
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J CELL BIOL 87 (2): A17-A17 1980
COGGIN S, KOCHERT G
FLAGELLAR
GROWTH AND REGENERATION IN THE LIFE-CYCLE OF VOLVOX-CARTERI
J CELL BIOL 87 (2): A39-A39 1980
BARCELLONA WJ, MCCRACKEN MD
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BRYANT JL, GREEN KJ, KIRK DL
TIME-LAPSE
CINEMICROGRAPHIC ANALYSIS OF MORPHOGENESIS IN WILD-TYPE AND MUTANT VOLVOX EMBRYOS
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BLAMIRE J, COTTRELL SF, TASHIMOVICH A
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STARR RC, ONEIL RM, MILLER CE
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1979
MARGOLISKAZAN H, BLAMIRE J
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MARGOLISKAZAN H, BLAMIRE J
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JAENICKE L, WAFFENSCHMIDT S
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KOCHERT G, CRUMP WJ
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BIRCHEM R, KOCHERT G
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HUSKEY RJ, SEMENKOVICH CF,
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SENESCENCE IN
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1977
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J CELL BIOL 75 (3): 719-730 1977
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NOLAND T, YATES I, KOCHERT G
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1976
MARGOLISKAZAN H, BLAMIRE J
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YATES I, KOCHERT G
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LEE WSB, KOCHERT G
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KIRK DL, KIRK MM
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MCCRACKEN MD, BARCELLONA WJ
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1975
YATES I, DARLEY M, KOCHERT G
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CYTOBIOS 12 (47-4): 211-223 1975
MEREDITH RF, STARR RC
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BRADLEY DM, CLAYBROOK JR
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HUSKEY RJ, CECIL
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F NAGARIENSIS
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EWART B
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KOCHERT G, YATES I
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J PHYCOL 10: 6-6 Suppl. S 1974
MEREDITH R
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BRADLEY DM, CLAYBROO.JR, GOLDIN HH
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MEREDITH R
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BRADLEY DM, GOLDIN HH, CLAYBROO.JR
HISTONE
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STARR RC, JAENICKE L
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KOCHERT G, YATES I
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J PROTOZOOL 21 (1): 121-125 1974
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PALL ML
EVIDENCE FOR GLYCOPROTEIN
NATURE OF INDUCER OF SEXUALITY IN VOLVOX
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1973
DARDEN WH
FORMATION AND
ASSAY OF A VOLVOX-FACTOR-HISTONE
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