Effects of caffeine and ARG7 locus on mutability of UV-treated photoreactivation-deficient mutants ofChlamydomonas reinhardtii

Forward streptomycin-resistant mutations and reverse mutations at the ARG7 locus after UV irradiation were studied in two photoreactivation-deficient mutants ofChlamydomonas reinhardtii, Phrl and Phr2. The mutant Phrl was more mutable than Phr2. Caffeine increased survival and reduced mutation rate of streptomycin-resistant mutations induced in both photoreactivation-deficient strains. Two different alleles of ARG7 locus (arg2 and arg7) were introduced into photoreactivation-deficient mutants. It was found that in the presence of both alleles, the frequency of mutants resistant to streptomycin was reduced. The reduction was more remarkable in the presence of arg2. But also under these conditions Phr1 was more mutable than Phr2.