SEX-PEPTIDE ACTIVATES JUVENILE-HORMONE BIOSYNTHESIS IN THE DROSOPHILA-MELANOGASTER CORPUS ALLATUM

Mating elicits two well-defined reactions in sexually matured females of many insects: reduction of receptivity and increased oviposition. T hese post-mating responses have been shown to be induced by factors sy nthesized in the reproductive tract of the adult male and transferred in the seminal fluid to the female during copulation. One of these fac tors, named sex-peptide (SP), has been identified in Drosophila melano gaster. Using an in vitro radiochemical assay, we show that synthetic sex-peptide considerably activates juvenile hormone III-bisepoxide (JH B(3)) synthesis in corpus allatum (CA) excised from Days 3 and 4 post- eclosion virgin females. Base levels are significantly lower at emerge nce (Day 0) than on subsequent days, and only weak stimulation is obta ined on Day 1, while none is obtained on Day 2, where maximal basal sy nthesis occurs. The CA of mated females cannot be stimulated further f or at least 7 days, but regain responsiveness by Day 10 after mating. Synthesis of JHB(3) stimulated by SP in vitro persists for at least 4 h after removal of the peptide. Development of responsiveness of the C A to SP in vitro is compared with development of the post-mating react ions of sex-peptide injected virgin females. Our results suggest that the CA is a direct target for SP in vivo and that sexual maturity is e stablished separately for the two post-mating reactions. (C) 1996 Wile y-Liss, Inc.