The vitellins (Vts) of insects are phosphoglycolipoproteins which serve as the major nutrient source for the developing embryo. Following its uptake into the oocyte via adsorptive endocytosis, Vt is stored in vesicles called yolk granules or platelets, variably processed and finally degraded in a controlled manner during embryo development. The mechanisms which regulate the processing of Vt and control the timing of the breakdown are unknown, as is the role of the yolk granule. Dr. Nordin proposes to investigate certain aspects of the postovulatory processing of Vt in Blattella germanica to increase our understanding of this phase of insect embryogenesis. The project has the following objectives: 1) Development of procedures for preparation of yolk vacuolar elements, particularly yolk granules, which have not been isolated from insects. 2) An assessment of vacuolar acidification in the processing and degradation of Vt in the egg. 3) Purification and characterization of two developmentally- expressed enzymes, a protease which participates in the postovulatory processing of this Vt and an acid/neutral phosphatase, whose activity correlates with the processing and which may facilitate Vt utilization. %%% During the maturation of the insect egg, protein in synthesized and stored as yolk. As much as 90% of the stored proteins in these eggs is vittelogenin. Much is known about the synthesis and uptake of this protein by the maturing oocyte. However very little is known about how they are broken down and utilized during embryogenesis.
