THE CHLAMYDOMONAS ZYGOSPORE - MUTANT STRAINS OF CHLAMYDOMONAS-MONOICABLOCKED IN ZYGOSPORE MORPHOGENESIS COMPRISE 46 COMPLEMENTATION GROUPS

Chlamydomonas monoica undergoes homothallic sexual reproduction in res ponse to nitrogen starvation. Mating pairs are established in clonal c ulture via flagellar agglutination and fuse by way of activated mating structures to form the quadriflagellate zygote. The zygote further ma tures into a dormant diploid zygote spore through a series of events t hat we collectively refer to as zygosporulation. Mutants that arrest d evelopment prior to the completion of zygosporulation hare been obtain ed through the use of a variety of mutagens, including ultraviolet irr adiation, 5-fluorodeoxyuridine, ethyl methanesulfonate, and methyl met hanesulfonate. Complementation analysis indicates that the present mut ant collection includes alleles affecting 46 distinct zygote-specific functions. The frequency with which alleles at previously defined loci hare been recovered in the most recent mutant searches suggests that as many as 30 additional zygote-specific loci may still remain to be i dentified. Nevertheless, the present collection should provide a power ful base for ultrastructural, biochemical, and molecular analysis of z ygospore morphogenesis and dormancy in Chlamydomonas.