Control of gametic differentiation and activity by light in Chlamydomonas reinhardtii

Laboratory strains of Chlamydomonas reinhardtii, which are descendants of a 1945 isolate by G.M. Smith (Harris 1989), were divided into two groups depending upon whether the vegetative cells require light to differentiate into gametes under ammonium ion-starved conditions. Light-dependent (LD) strains were unable to become gametes in the dark, while light-independent (LI) stains could do so. All the wild-type strains isolated recently from the field showed light-dependency, suggesting that the LD-phenotype is the wild-type. The LD-cells failed to acquire flagellar agglutinability, to accumulate cell body agglutinins, or to form mating structures in the dark, but did so rapidly after transfer to light. Moreover, the light-induced LD-gametes, but not the LI-gametes, lost their mating ability, cell body agglutinins, and mating structures after transfer to darkness, indicating that the LD-cells require light not only for gametic differentiation but also for maintenance of gametic activi