Variation in sex-, stage- and tissue-specific expression of the amylase genes in Drosophila ananassae.

Expression of the amylase multigene family of Drosophila ananassae was investigated in third-instar larvae and adults. A developmental differentiation was found between the Amy1-2 and Amy3-4 gene clusters, the former being preferentially expressed in larvae, the latter in adults. During adult life, we observed a decrease in Amy1-2 expression in males of certain strans. We have raised some arguments for the existence of trans-active regulators, acting as repressors of Amy1-2 in adults. The putative repressors might exhibit a geographical polymorphism, with a fixed active form in Pacific regions and a polymorphic pattern in Africa, thus increasing the diversity observed in adult amylase phenotypes. A clear differentiation between the two gene clusters was also found in tissue-specific activity along the third-instar larval midgut. In the anterior midgut, only Amy1-2 is active, while both gene groups are expressed in the posterior midgut, with an additional subzonation within it.