EFFECTS OF CAFFEINE AND ARG7 LOCUS ON MUTABILITY OF UV-TREATED PHOTOREACTIVATION-DEFICIENT MUTANTS OF CHLAMYDOMONAS-REINHARDTII

Forward streptomycin-resistant mutations and reverse mutations at the ARG7 locus after UV irradiation were studied in two photoreactivation- deficient mutants of Chlamydomonas reinhardtii, Phr1 and Phr2. The mut ant Phr1 was more mutable than Phr2. Caffeine increased survival and r educed mutation rate of streptomycin-resistant mutations induced in bo th 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 frequ ency of mutants resistant to streptomycin was reduced. The reduction w as more remarkable in the presence of arg2. But also under these condi tions Phr1 was more mutable than Phr2.