Sexual development in the homothallic green alga Chlamydomonas monoica Strehlow

Abstract

Sexual development in the homothallic green alga Chlamydomonas monoica strehlow van den Ende, H. Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. Abstract In Chlamydomonas monoica, cell division and mating are interdependent processes, since under gametogenic conditions only newly born cells are mating competent. By refeeding nitrogen-starved cells with nitrate or ammonium ions, cell division and mating were synchronized. The mating competence of the progeny cells was dependent on the amount of the nitrogen source parent cells were refed, with an optimum around 0.1 btmol.105 cells. A second treatment with nitrate inhibited gametogenesis, but only when applied during the first part of the cell cycle, suggesting that an essential part of sexual development takes place during this period. During the latter part of the cell cycle, cells required light to acquire mating competence.

Light is a crucial signal for zoosporogenesis and gametogenesis in some green microalgae

“…was induced after 16 h darkness (Bakker, 1995) and production of gametes in Chlorococcum echinozygotum also occurred in darkness (O'Kelley, 1983). In contrast, in Chlamydomonas monoica, experimentally applied darkness inhibited gamete mating during the later phase of the cell cycle (van den Ende, 1995). In the prasinophyte Nephroselmis olivacea, sexual cell fusion started at the onset of the light period, following mixing of the two mating types, and peaked 1 h later (Suda et al, 1989).…”

“…However some green microalgae also produce zoospores or gametes. Sexual reproduction (isogamy, anisogamy or oogamy) has been described in only a few genera, the best studied being Atractomorpha (Hoffman, 1984;Cáceres et al, 1997), Chlamydomonas (Sager & Granick, 1954;Nečas, 1982;Beck & Acker, 1992;van den Ende, 1995), Chlorococcum (O'Kelley, 1983, Chlorogonium (Nozaki et al, 1995), Dunaliella , Golenkinia (Iyengar & Balakrishnan, 1956;Moestrup, 1972), Lobochlamys and Oogamochlamys (Pröschold et al, 2001), Nephroselmis (Suda et al, 1989(Suda et al, , 2004, Pediastrum (Komárek & Fott, 1983;Wilcox & Floyd, 1988), and Tetraspora (Rhodes, 1967).…”

CHLAMYDOMONAS AS A MODEL ORGANISM

“…In C. moewusii, C. eugametos, C. monoica, and some other Chlamydomonas species, flagellar contact is followed initially by fusion only at the extreme anterior ends of the cells, and the partner cells swim about for several hours as a "visa-vis" pair before full cell fusion occurs (229). This distinction in the mating process is probably a very fundamental character separating different ancestral lineages within the green algae.…”

“…Sexual cycles have been described in relatively few Chlamydomonas species, so this has not been used as a character in traditional taxonomy. The overall process of recognition, signal transduction, and cell fusion in C. eugametos resembles that of C. reinhardtii in many ways, however, and a substantial body of literature exists on the sexual cycle in this species (see 229). Zygote-specific transcripts appear within minutes of gamete fusion (121 and references cited therein).…”

ZOOSPOROGENESIS, MORPHOLOGY, ULTRASTRUCTURE, PIGMENT COMPOSITION, AND PHYLOGENETIC POSITION OF TRACHYDISCUS MINUTUS (EUSTIGMATOPHYCEAE, HETEROKONTOPHYTA)1

“…Nitrogen depletion was found to be a prerequisite for gametogenesis in species such as Chlamydomonas reinhardtii (Sager and Granick 1954, Weissig and Beck 1991, Beck and Acker 1992, Rodriguez et al. 1999), Chlamydomonas monoica (Vandenende 1995), Oedogonium hatei (Chaudhary and Singh 1988), and C. echinozygotum (O`Kelley 1983, 1984). In contrast, nitrogen starvation inhibited production of zoospores in T. minutus , which indicates that the processes of zoospore development in this species are regulated differently as compared to the gametogenesis in Chlorophyceae.…”