Dosage compensation and dietary glucose repression of larval amylase activity in Drosophila miranda.

The functional locus for alpha-amylase (Amy) in Drosophila miranda is in the evolutionarily new X2 chromosome. X2 evolved from an autosome in response to an ancestral autosome-Y translocation that gave rise to the "neo-Y" chromosome of this species. Y-linked Amy, if still present in the ancestrally translocated element, is unexpressed. Dosage compensation for amylase activity was examined in larvae of the S 204 strain. Since dietary glucose is known to repress Amy expression in Drosophila melanogaster, dosage compensation of amylase activity in male larvae of D. miranda was tested by rearing larvae of both sexes on yeast diets with or without a glucose supplement. The WT 10 strain of Drosophila persimilis, a sibling species in which Amy is autosomally linked, was used as a reference for tests of amylase activity differences between the sexes. On the diet with glucose, Amy expression was repressed in both WT 10 and S 204 larvae and male larvae of S 204 displayed dosage compensation for amylase activity. On the nonrepressing diet consisting of yeast alone, S 204 continued to display dosage compensation.