KOUFOPANOU V, BELL G

SOMA AND GERM - AN EXPERIMENTAL APPROACH USING VOLVOX
P ROY SOC LOND B BIO 254 (1340): 107-113 NOV 22 1993

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 OCT 7 1993

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 Jordan, has short (12-bp) terminal inverted repeats and creates a 3-bp target site duplication, like some higher plant transposons of the classic type. Contained within the first 200 bp of one end of the element are 55-bp inverted repeats, one of which begins with the terminal inverted repeat. Revertants of the transposon insertion into the nitA locus were obtained at a rate of approximately 10(-4) per Volvox embryo per generation. In each revertant examined, all transposon sequences were completely excised, but footprints containing both sets of duplicated bases, in addition to three to nine extra bases, were left behind. Jordan contains no significant open reading frames and so appears to be nonautonomous. DNA gel blot analysis indicates that Jordan is a member of a large family of homologous elements in the Volvox genome. We have isolated and characterized several of these homologs and found that they contain termini very similar to those of Jordan. Efforts to utilize Jordan and its homologs as tools to tag and clone developmentally interesting genes of Volvox are discussed.

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 JUL 15 1993

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 MAR 22 1993

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.

HOLLOWDAY ED

CEPHALODELLA-EDAX SP-NOV A ROTIFER PARASITIC IN THE MOTILE COLONIAL ALGA UROGLENA-VOLVOX EHRENBERG
HYDROBIOLOGIA 255: 445-448 APR 16 1993

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 pacifica Kylin.

HOOPS HJ

FLAGELLAR, CELLULAR AND ORGANISMAL POLARITY IN VOLVOX-CARTERI
J CELL SCI 104: 105-117 Part 1 JAN 1993

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 FEB 1 1993

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.