CHARACTERIZATION OF BLUE-LIGHT SIGNAL-TRANSDUCTION CHAINS THAT CONTROL DEVELOPMENT AND MAINTENANCE OF SEXUAL COMPETENCE IN CHLAMYDOMONAS-REINHARDTII

Blue light induces the differentiation of Chlamydomonas reinhardtii pr egametes to gametes. The light-induced conversion of pregametes to gam etes is protein synthesis dependent and proceeds only after a lag phas e. Upon incubation in the dark, gametes lost their mating ability, res ulting in dark-inactivated gametes. Reillumination rapidly restored ma ting competence and this was shown to be independent of protein synthe sis. Apparently, differentiation and maintenance of gametic competence are both regulated by light. Whether one or two light-activated signa l pathways are involved was investigated using pharmacological compoun ds that affect signal transduction. Compounds that affected pregamete- to-gamete conversion affected the expression of a gamete-specific gene in a similar fashion. Other drugs affected only dark-inactivated game tes, suggesting that reactivating gametes requires a separate signalin g pathway. Combined treatments provided evidence for the consecutive a ction of a phosphatase and a protein kinase C-like kinase in the light -induced reactivation process.