Gametogenesis of Chlamydomonas in the dark

When cells of each mating type of Chlamydomonas sp. (Toyonakastrain) were transferred to a nitrogen-free medium and culturedat low temperature (10?C) for 10 to 12 hr, they showed matingactivity even in the dark. The highest activity observed inthe dark, at about 10?C, was similar to that in the light at20?C. Induction in the dark was suppressed by oxygen deficiency.It was also inhibited by addition of 1 to lOmin concentrationsof nutritional nitrogen compounds such as ammonium, nitrateor urea, and of cycloheximide (2 to 20 µg/ml), but notby addition of chloramphenicol, dihydrostreptomycin or spectinomycin.On the other hand, it was slightly promoted by addition of theophylline,aminophylline, cAMP, DB-cAMP, kinetin and abscisic acid. ¹Present address: Department of Animal Virology, The ResearchInstitute for Microbial Diseases, Osaka University, Suita, Osaka565, Japan. (Received June 3, 1976; )