Role of phenol oxidases and thyrosine hydroxylase in control of dopamine content in Drosophila virilis under normal conditions and heat stress

The activity of thyrosine hydroxylase (TH) was studied in adults of D. virilis lines resistant and sensitive to heat stress, and in their F 1 hybrids under normal conditions and heat stress. It was demonstrated that in the resistant Une TH activity is higher than in the sensitive one under normal conditions; that the former line is dominant for the trait; and that the gene(s) controlling the activity level of TH under normal conditions is not sex-linked. It was also demonstrated that 30 min of heat stress produces a fall in TH activity in the resistant line, and that, after 120 min of the stress, the activity of the enzyme increases. TH activity does not alter in the sensitive line under heat stress; this line is dominant for the trait and the gene(s) controlling the activity level of the enzyme under stress is not sex-linked. Phenol oxidase activity was also examined in these lines under normal conditions and short-term heat stress. It was shown that neither mono, nor diphenol oxidase activities change under heat stress. It was found that lines of D. virilis resistant and sensitive to heat stress differ in diphenol oxidase activity under normal conditions. Genetic analysis of these differences revealed that they are controlled by a single gene (or a group of closely linked genes). The gene is located on the X-chromosome.