Structure and expression of a Drosophila male accessory gland gene whose product resembles a peptide pheromone precursor.

The accessory gland of male insects is a genital tissue that secretes many components of the ejaculatory fluid, some of which affect the female's receptivity to courtship and her rate of oviposition. We have examined the structure and expression of two tightly linked genes that are expressed exclusively in the male accessory glands of adult Drosophila melanogaster. The two genes are transcribed from the same strand of DNA, and are separated by 20 bases. Both genes are regulated by the sex determination hierarchy and are expressed in the absence of germ cells. Immunological analysis reveals the protein products of at least one of these genes in the secretion of the accessory gland. The proteins are transferred to the female fly during copulation and are rapidly altered in the female genital tract. The predicted sequence of one protein has features of a peptide hormone precursor, and a region in which 11 of 17 amino acids are identical to egg-laying hormone (ELH) of the California sea hare, Aplysia californica.