EVOLUTION OF THE RESPONSE PATTERNS TO DIETARY CARBOHYDRATES AND THE DEVELOPMENTAL DIFFERENTIATION OF GENE-EXPRESSION OF ALPHA-AMYLASE IN DROSOPHILA

Intraspecific variation of alpha-amylase activity in D. melanogaster a nd D. immigrans, which is distantly related to D. melanogaster, and in terspecific variation of alpha-amylase activity in 18 Drosophila speci es were examined. The amount of intraspecific variation of alpha-amyla se activities measured in terms of coefficient of variation in D. mela nogaster and D. immigrans was one-half and one-tenth or less: respecti vely, of the interspecific variation in 18 Drosophila species. We also surveyed the response patterns of alpha-amylase activity to dietary c arbohydrates at the larval and adult stages, The levels of alpha-amyla se activity depended on both repression by dietary glucose (glucose re pression) and induction by dietary starch (starch induction). In gener al, our data suggest that glucose repression was conserved among speci es at both stages while starch induction was mainly observed in larvae , although the degree of the response depended on species. In D. leban onensis lebanonensis and D. serrata, larvae expressed electrophoretica lly different alpha-amylase variants (isozymes) from those of adult fl ies. These results may suggest that the regulatory systems responsible both for the response to environment and developmental expression are different among species in Drosophila.