Vitellogenesis in diapausing and mutant Drosophila melanogaster: further evidence for the relative roles of ecdysteroids and juvenile hormones

The juvenile hormones (JHs) have long been believed to be key elements of the regulation of vitellogenesis in Drosophila melanogaster. This essential role for JH was challenged in Richard et al. (Journal of Insect Physiology 44 (1998)) in a novel model of the endocrine control of vitellogenesis. Further evidence supporting this proposed model and for understanding yolk protein (YP) production and uptake in JH-deficient conditions is presented here. Pre-vitellogenic diapause in the Canton-S strain was terminated within 4 days by the injection of 0.1 ng 20-hydroxyecdsyone; the application of 1 μg JH III failed to elicit a response suggesting once more that ecdysteroids may be the more important agent. Nevertheless, this dose of JH III did reverse the delay associated with the onset of reproductive development of the JH-deficient mutant ap56f in a manner consistent with the proposed role for JH of stimulating early YP synthesis by ovarian follicle cells. Similarly, JH III application to ap4 females also stimulated a degree of ovarian development. A high affinity JH III binding factor (KD=1.5 nM) in whole body extracts was quantified by equilibrium dialysis. Binding levels were greater in Canton-S females than in ap56f females though in ap56f binding could be stimulated within 18 h of eclosion by the application of 1 μg JH III. Ovaries from ap56f and Canton-S failed to produce any JH-like compounds. These data are discussed in the context of our model for the endocrine control of vitellogenesis in Drosophila.