Vitellin (Vt) is a phosphoglycolipoprotein which serves as the primary nutritive source for the insect embryo. Following uptake into the oocyte, Vt is stored in yolk granules, variably processed and finally degraded in a controlled manner during embryo development. The mechanisms responsible for initiating and timing Vt breakdown are unknown. Previous work from this laboratory with Blattella germanica identified a processing proteinase involved in Vt degradation and showed that its activation in vivo is correlated temporally with the acidification of the yolk granules and changes in their size. Because these events may be interrelated physiologically in the regulation of Vt degradation, the following studies will be carried out: the identification of the mechanism responsible for yolk granule acidification and how that mechanism is activated, the purification and characterization of the processing proteinase, and the investigation of vitellophage and yolk granule morphology during early embryo development.
