A somatic reproductive organ enhancer complex activates expression in both the developing and the mature Drosophila reproductive tract.

The Glucose dehydrogenase (Gld) gene is highly expressed in the mature Drosophila reproductive tract. Unlike several other Drosophila genes which function in reproductive physiological processes, Gld is also expressed extensively in the developing reproductive tract during metamorphosis. Proximal promoter elements drive Gld expression in a variety of tissues throughout development, but not in the reproductive tract. Herein, we have identified a somatic reproductive organ enhancer complex (SREC) containing multiple redundant enhancer modules in Gld intron I (+639 to +3906 nt). The SREC, in combination with the Gld promoter, activates beta galactosidase reporter gene expression in both the developing and the mature reproductive tract. The SREC activates a heterologous hsp70 promoter in the ejaculatory duct, but not in other reproductive tract tissues, suggesting that the SREC acts synergistically with Gld promoter proximal elements. Through deletion analysis we have delimited a 361-nt region of the SREC that is involved in ejaculatory duct/oviduct-specific expression. The ejaculatory duct/oviduct enhancer retains the ability to activate expression in both the developing and the mature reproductive tract, suggesting that the same basic enhancer elements activate Gld expression during metamorphosis and in adults. A model of the evolution of Gld expression in the ejaculatory duct and oviduct is presented.