The roles of juvenile hormone, ecdysone and the ovary in the control of Drosophila vitellogenesis

Abstract

Vitellogenesis in Drosophila is regulated by the sex-determination gene pathway, the hormones ecdysone and juvenile hormone and the availability of nutrients. In this paper I show that the nutritional regulation is unlikely to be mediated via titres of ecdysone or juvenile hormone. Starved flies do not have reduced juvenile hormone or ecdysteroid titres. I show that flies without ovaries have normal levels of free ecysteroids after 2 days suggesting that the ovaries do not produce substantial quantities of free ecdysteroids continuously in the adult for use in regulating vitellogenesis, however, they probably do contribute to the whole body titre in mature flies since titres do become less in ovary-less flies at 3 days. This is consistent with data on the measurement of ecdysteroids produced by ovaries in vitro. Flies defective in vitellogenesis, namely apterous 4, long thought to be a juvenile hormone mutant, are shown by gas chromatography/mass spectrometry to have a reduced juvenile hormone level. The interactions between these hormones, the genetic control of yolk-protein transcription, the ovary and the actual occurrence of vitellogenesis are discussed.