NUTRITIONAL RESPONSE IN A DROSOPHILA YOLK PROTEIN GENE PROMOTER

The yolk protein genes (yps) of Drosophila melanogaster are only expre ssed in the ovary and fat body of female flies if they are supplied wi th proteinaceous food. This nutritional response is specific to the yp genes. We have used transgenic flies transformed with a series of con structs bearing deletions in the upstream region of the yp1 and yp2 ge nes attached to a reporter gene to search for DNA sequences responsibl e for the nutritional induction specific for yp1 and yp2 genes. Severa l regions were shown independently of each other to confer nutritional regulation on the expression of the yp1 and yp2 genes. This regulatio n can be induced both on the yp promoter and the heterologous Drosophi la heat-shock 70 (hsp70) promoter. The redundancy of sequences conferr ing a nutritional response on the yp genes is similar to that observed for the female specificity of these genes and suggests that several D NA binding proteins interact to provide the correct regulation of thes e genes. These results suggest that nutrition acts to modify the level of a trans-acting factor in the fat body. Northern blot analysis show ed that the transcript levels from the dsx gene are not affected by nu trition, indicating that the response is not mediated via the dsx gene .