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