Evidence for redundancy but not trans factor-cis element coevolution in the regulation of Drosophila Yp genes

In Drosophila melanogaster and the endemic Hawaiian species D. grimshawi th ree Yolk protein (yp) genes are expressed in a similar sex- and tissue-spec ific pattern. In contrast, DNA sequence comparisons of promoter/enhancer re gions show low levels of similarity. We tested the functional significance of these observations by transforming D. melanogaster-with the genomic regi on that includes the divergently transcribed D. grimshawi DgYp1 and DgYp2 g enes; we found that the introduced genes were expressed in female fat body and in ovaries but not in males. Moreover, we found D. grimshawi proteins i n the hemolymph and accumulating in ovaries. Using reporter constructs we s howed that the intergenic region from D. grimshawi was sufficient to drive accurate expression, but some low level of ectopic expression was seen in m ales. Transforming D. melanogaster with constructs bearing deletions within the D. grimshawi intergenic region revealed only subtle effects in the ove rall level of expression, suggesting a high level of redundancy. Testing mu tants in the sex-specific regulator doublesex revealed that it is capable o f repressing the DgYp genes in males. Together, these data show that D. mel anogaster trans-acting factors can regulate the in vivo pattern of DgYp exp ression and support the notion of a redundant and complex system of cia-act ing elements.