Coevolution of the glucose dehydrogenase gene and the ejaculatory duct in the genus Drosophila

The glucose dehydrogenase gene (Gld) in Drosophila melanogaster exhibits aunique spatial and temporal pattern of expression. GLD expression switchesfrom a non-sex-limited state at the pupal stage to a male-limited state atthe adult stage. At the adult stage, the enzyme is restricted to theejaculatory duct. Within the genus Drosophila, the ejaculatory duct hasundergone a simple morphological divergence. In order to determine whethercorrelated changes in GLD expression had occurred, GLD activity during thepupal and adult stages was determined for several Drosophila species. Itwas found that virtually all of the species exhibit pupal GLD activity,whereas only those species with an expanded ejaculatory duct expressmale-limited GLD. The results of interspecific genital imaginal disctransplantation experiments indicate that the expanded morphology and GLDexpression do not require any species- or sex-specific diffusible factors.An apparent regulatory polymorphism exists within the D. takahashii specieswith respect to male-limited GLD expression.