Photoresponses of wild-type and mutant dikaryons ofChlamydomonas

Photoaccumulation and random motility of wild-type and mutant gametes and dikaryons ofChlamydomonas reinhardtii were evaluated with quantitative assays and compared with those of vegetative cells. Gametes exhibited behavior similar to that of vegetative cells. Dikaryons constructed from (+) and (−) wild-type gametes exhibited strong photoaccumulation in the presence of a stimulus and normal random swimming in red light, which shows that the activity of flagella and other components from two cells can be integrated and coordinated to permit appropriate behavior. Dikaryons from crosses of the wild type with mutants exhibited intermediate photoaccumulation. suggesting that neither phenotype is dominant. In contrast, crosses between an abnormally swimming mutant and normally motile strains showed that wild-type swimming was dominant. Partial complementation of mutant photoresponse phenotypes occurred in some crosses, but recovery of fully normal behavior was not observed.