Hormonal regulation of yolk protein uptake by vitellogenic oocytes in diapausing and mutant female Drosophila melanogaster.

Presented to Complex Clocks. International conference in honour of Professor David Saunders. Held Edinburgh, March 20-24, 2000.

David S. Richard, Jennifer M. Jones, Matthew Gilbert, Michael Barbarito, Dana Brannigan and Stephen Fischer. Department of Biology, Susquehanna University, Selinsgrove, PA 17870-1164. USA.

Many Diptera undergo photoperiodic diapause induction associated with an arrest of the endocrine system at species-specific points of the life cycle. Upon exposure to short day photoperiods at low temperatures, female Drosophila melanogaster exhibit a pre-vitellogenic ovarian diapause (Saunders et al., 1989) associated with suppressed ovarian ecdysteroid production and corpus allatum juvenile hormone (JH) production. The application of JH III or JHB3 to diapausing females results in diapause termination, as does the injection of 20­hydroxyecdysone though the latter results in the more rapid onset of vitellogenesis. Diapause termination by temperature upshift is associated with an increase in ecdysteroid, but not JH production prior to the onset of vitellogenesis. The application of JH III to otherwise apparently JH-deficient ap56f females rescues a 6-h delay in vitellogenesis associated with this allele indicating that JH may stimulate follicle cell (early) YP synthesis. Preliminary data on the production of JH by ovaries and other tissues support the contention that ap56f females are indeed JH-deficient. Ovarian ecdysteroids have been shown previously to regulate late YP synthesis by the fat body (Bownes 1989). Immuno-staining for receptor mediated endocytosis-associated proteins (clathrin, a-adaptin and YP-receptor, YPR) show localization to those nurse cells immediately adjacent to vitellogenic stage 9-13 oocytes. a-Adaptin and YPR levels increase during diapause termination suggesting that ecdysteroids and not JH may regulate them. These observations support modifications of the mechanisms for the endocrine regulation of vitellogenesis. (Supported in part by NIH GM/OD54905 to DSR).

Bownes,M. (1989) The roles of juvenile hormone, ecdysone and the ovary in the control of Drosophila vitellogenesis. J. Insect. Physiol. 35,409-413.

Saunders,D.S., Henrich,V.C. and Gilbert,L.I. (1989) Induction of diapause in Drosophila melanogaster :Photoperiodic regulation and the impact of arrhythmic mutations on time measurement. Proc. Natl. Acad. Sci. USA. 86, 3748-3752.