title: Ecdysteroids regulate yolk protein uptake by Drosophila melanogaster oocytes.
abstract: Juvenile hormones (JHs) are thought to drive the regulation of yolk protein uptake by ovaries in Drosophila melanogaster. However, the level of JH production in a mutant stock (ap(56f)) is depressed yet the flies are normally vitellogenic. The production of ecdysteroids by these ap(56f) ovaries in vitro is elevated above that of wild-type ovaries. The incubation of wild-type ovaries in the presence of 0.1mM JHB(3) increased ecdysteroid biosynthesis only during the first 18h following eclosion. Female Drosophila melanogaster undergo a pre-vitellogenic reproductive diapause when exposed to low temperature (11 degrees C) and a short-day photoperiod (L12:D12). The rate of ecdysteroid synthesis by the ovaries, but not JH production, increased within 12h of a temperature upshift to 25 degrees C from a basal level of 20+/-1pg/10 pair of ovaries/5h to a sustained level of 150+/-20pg/10 pair/5h. Vitellogenic oocytes were noted in all females within 12h of this temperature upshift. Diapause was also terminated by the injection of 1&mgr;g of 20-hydroxyecdysone into the abdomens of diapausing females as determined by an increase in ovary size, and the appearance of vitellogenic oocytes as compared to controls. These results are consistent with a revised model for the regulation of yolk protein uptake by ovaries in which ecdysteroids, and not JHs, play the prominent role.
authors.affiliation: Department of Biology, University of North Carolina at Chapel Hill, Coker Hall CB# 3280, Chapel Hill, USA
authors.forename: L I.
authors.initials: LI
authors.lastname: Gilbert
authors.forename: R B.
authors.initials: RB
authors.lastname: Serafin
authors.forename: N L.
authors.initials: NL
authors.lastname: Watkins
authors.forename: D S.
authors.initials: DS
authors.lastname: Richard