Gametogenesis in Liquid Cultures of Chlamydomonas eugametos

Tomson, A. M.; Demets, R.; Bakker, Norbert; Stegwee, D.; Ende, H. van den

doi:10.1099/00221287-131-7-1553

Cited by 13 publications

(13 citation statements)

References 16 publications

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“…The protoplast divides into a number of daughter cells which are released after enzymic dissolution of the mother cell wall. In C. eugametos, vegetative reproduction is terminated, when the culture medium runs out of nutrients, by a gametogenic cell division (Tomson et al, 1985). To take a closer look at the division cycle of C. eugametos, we tried to synchronize the cells by the method of Bernstein, which was successfully applied to the closely related species C. moewusii (Bernstein, 1960 ;Kates & Jones, 1964), and is still frequently used to synchronize C. reinhardtii (Surzycki, 1971 ;Cavalier-Smith, 1974;Spudich & Sager, 1980).…”

Section: Introductionmentioning

confidence: 99%

Synchronization of the Cell Division Cycle of Chlamydomonas eugametos

et al. 1985

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A description is given of the vegetative growth of Chlamydomonas eugametos in liquid cultures. When a circadian light/dark regime is applied, cell division takes place during the dark periods and the release of the daughter cells is phased round the dark/light transitions. However, as long as the cultures are agitated, only a fraction of the cells divides during any dark period. The mother cells stick firmly to the surface of the culture vessels, making it possible to separate them from the non-dividing cells. They release daughter cells that show cell cycles of 1 x 24 h, 2 x 24 h and longer. Only in static cultures do all cells divide synchronously every 24 h. To explain these results, a correlation is postulated between the chance of settling and the length of the division cycle.

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Section: Introductionmentioning

confidence: 99%

Synchronization of the Cell Division Cycle of Chlamydomonas eugametos

et al. 1985

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“…The cells that are sensitive to stimulation of agglutinability by flagellar contacts are sexually competent cells that underwent gametogenesis in response to nutrient deficiency (19). Besides, it has been established that there is no mutual influence of the mating types on vegetative development or gametogenesis in C. eugametos ( 19).…”

Section: Resultsmentioning

confidence: 99%

“…On the other hand, Mesland (12) demonstrated that mt-gametes bind more mt+ gametes than The mutual contact-induced stimulation must not be confused with contact-induced gametogenesis that occurs in some unicellular algae (22). The cells that are sensitive to stimulation of agglutinability by flagellar contacts are sexually competent cells that underwent gametogenesis in response to nutrient deficiency (19). Besides, it has been established that there is no mutual influence of the mating types on vegetative development or gametogenesis in C. eugametos ( 19).…”

Section: Resultsmentioning

confidence: 99%

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Cellular Interactions during the Mating Process in Chlamydomonas eugametos

Tomson¹,

Demets²,

Sigon³

et al. 1986

Plant Physiol.

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ABSTRACI A method to determine the mating competence of Chiamydomonas eugametos was developed. The contribution of each mating type in the pair formation was investigated using asymmetric gamete mixtures. It was established that pair formation is not mediated by a pheromonal attraction mechanism between partner gametes, but depends on collision chances. On the other hand, it was demonstrated that during transient contacts between partner gametes the flagellar agglutinability of both partners is stimulated, evidently to prepare a successful mating. The plus mating type was generally less agglutinable than the minus mating type and was a rate-limiting factor in the mating process.Chlamydomonas eugametos is a biflagellate unicellular green alga, reproducing vegetatively by sporulation. Its 6,9,21,22). C. moewusii var. rotunda is a well-known exception to this reasoning because it shows chemotaxis between equally motile isogametes. However, the substances produced by the attracting minus mating type also attract interspecifically both mt+ and mt-gametes of C. eugametos (20).In this piiper we reinvestigated the mating process in C. eugametos, using different approaches. Our conclusion is that chemotaxis is not involved in the mating of C. eugametos, but that partner gametes meet via random collisions. We demonstrate that a successful pair formation is prepared by transient contacts, during which the flagellar agglutinability of both partners is stimulated. MATERIALS AND METHODSCell Cultures. Chlamydomonas eugametos strains UTEX 9 (mating type plus, mt+) and UTEX 10 (mating type minus, mt-) from the Algal Collection at the University of Texas (Austin) were grown in Petri dishes on an agar-containing medium on a 12 h light/12 h dark regime as described by Mesland (11). Gamete suspensions were obtained by flooding 2-week-old cultures with 20 ml distilled H20 just before the start of the dark period; the gametes were harvested at the beginning of the following light period. To determine cell densities, samples fixed with glutaraldehyde (final concentration 1.25% v/v) were counted in a haemocytometer. Gamete suspensions were diluted with cell-free medium. This was obtained by centrifuging a parallel batch ofgamete suspension and filtering the supernatant through a 0.8 ,um Millipore filter.

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“…While depletion of nitrogen is specifically required to induce gamete formation in C. reinhardtii other nutrient stresses may initiate differentiation in C. eugametos [94], but this issue has not been thoroughly explored. It is possible that a common metabolic signal triggers the developmental programme in both, or even all, species of Chlamydomonas.…”

Section: Environmental Signals For Gametogenesmentioning

confidence: 99%

Signal transduction in the sexual life of Chlamydomonas

Quarmby

1994

Plant Mol Biol

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Several signal transduction pathways play important roles in the sexual life cycle of Chlamydomonas. Nitrogen deprivation, perhaps sensed as a drop in intracellular [NH4+], triggers a signal transduction pathway that results in altered gene expression and the induction of the gametogenic pathway. Blue light triggers a second signalling cascade which also culminates in gene induction and completion of gametogenesis. New screens have uncovered several mutants in these pathways, but so far we know little about the biochemical events that transduce the environmental signals of nitrogen deprivation and blue light into the changes in gene transcription that produce gametes. Cell-cell contact of mature, complementary gametes elicits a number of responses that prepare the cells for fusion. Contact is sensed by the agglutinin-mediated cross-linking of flagellar membrane proteins. An increase in [cAMP] couples protein cross-linking to the mating responses. In C. reinhardtii the cAMP signal appears to be generated by the sequential stimulation of as many as 3 distinct adenylyl cyclase activities. Although the molecular mechanisms of adenylyl cyclase activations are poorly understood, Ca2+ may play a role. Most of the mating responses appear to be triggered by a cAMP-dependent protein kinase, but here too, Ca2+ may play a role. Numerous mutants are facilitating studies of the signalling pathways that trigger the mating responses. Cell fusion triggers another series of events that culminate in the expression of zygote specific genes. The mature zygote is sensitive to a light signal which stimulates the expression of genes whose products are essential for germination. The signal transduction pathways that trigger zygospore formation and germination are ripe for investigation in this experimentally powerful system.

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Gametogenesis in Liquid Cultures of Chlamydomonas eugametos

Cited by 13 publications

References 16 publications

Synchronization of the Cell Division Cycle of Chlamydomonas eugametos

Synchronization of the Cell Division Cycle of Chlamydomonas eugametos

Cellular Interactions during the Mating Process in Chlamydomonas eugametos

Signal transduction in the sexual life of Chlamydomonas

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