Ecdysteroids drive the uptake of yolk proteins by oocytes from diapausing Drosophila melanogaster.

Jennifer M. Jones*, Michael R. Barbarito and David S. Richard, Department of Biology, Susquehanna University, Selinsgrove, PA 17870-1164.


Juvenile hormones (JHs) have long been thought to drive ovarian yolk protein (YP) uptake in Drosophila melanogaster, and ecdysteroids have been considered of secondary importance to the uptake process. However, recent studies have demonstrated that the levels of JH production in a mutant stock (apterous56f) are depressed yet the flies are vitellogenic. The presence of an approximately 12 to 20h delay in the onset of YP uptake in these flies has been confirmed. Female D. melanogaster undergo a pre-vitellogenic reproductive diapause when exposed to an L12:D12 photoperiod at 11oC or lower. Diapause is characterized by very low levels of JH and ecdysteroid production. Ecdysteroid production by the ovaries, but not JH production by the corpus allatum, increased sevenfold within 12 h of a temperature upshift to 25oC and vitellogenic oocytes were noted in all females. Diapause was terminated, and vitellogenesis initiated, in a dose dependent manner by the injection of 23ng20-hydroxyecdysone in MEM into the abdomens of diapausing females. YP uptake was noted in the injected females between 4 and 5 days after the injections. These results are consistent with a proposed new model for the regulation of yolk protein uptake by ovaries in which ecdysteroids, and not JHs, play the prominent role. (Supported in part by NIH GM/OD54905).