Tyrosine decarboxylase and dopa decarboxylase in Drosophila virilis under normal conditions and heat stress: genetic and physiological aspects.

The activity of tyrosine decarboxylase (TDC) and dopa decarboxylase (DDC) was studied in adults of two lines of Drosophila virilis, contrasting in their reaction to stress conditions. Differences were found in the activity of both enzymes between individuals of the examined lines. Genetic analysis of these differences was made. Each of the two enzymes was found to be controlled by a single gene or, possibly, by a block of closely linked genes. The gene responsible for TDC activity is located on one of the autosomes (excluding chromosome II). DDC activity in D. virilis is regulated by a gene located, apparently, on chromosome II. Adults of the line responding to stress by a stress reaction (r-line) were shown to react to a short-term heat stress (38 degrees C, 60 min) by a decrease in TDC activity. TDC activity in flies of the line incapable of the stress reaction (nr-line) did not alter in such conditions. DDC activity of adults of both lines was found to be unchangeable under stress conditions.