THE VITELLIN-PROCESSING PROTEASE OF BLATTELLA-GERMANICA IS DERIVED FROM A PRO-PROTEASE OF MATERNAL ORIGIN

Proteolytic processing of vitellin in Blattella germanica embryos is a ccomplished by activation of a yolk-borne cysteine protease (Mr 29 000 ) derived from a pro-protease precursor of Mr 40 000 (Liu et al., 1997 ). In the present study, fat body, ovaries and embryos of different de velopmental stages were examined immuno-cytochemically with purified m urine anti-proprotease antibodies (Liu, 1995) to determine the intrace llular location of the pro-protease. Proenzyme was detected in discret e secretory granules of the fat body and in large lysosome-like vesicl es of both the follicle cell cytoplasm and the cortical ooplasm of pre vitellogenic ovarian follicles. In vitellogenic oocytes, coated pits a nd vesicles are scantily labelled for proprotease and no clear gold pa ttern could be discerned over the yolk granules. During embryonic deve lopment, pro-protease is associated with some, but not all, yolk granu les. In newly-ovulated eggs (day 0), pro-protease is either distribute d over the entire granule or confined to some internal vesicles. As de velopment proceeds, it becomes associated with almost every yolk granu le and restricted to the superficial layer. By day 6, pro-protease is evident over all yolk granules but the intensity of reaction has great ly diminished, due probably to conversion of the pro-protease to the m ature enzyme. Yolk granules are flanked along their margin by vesicles that are stained after zinc-osmium fixation. This observation suggest s that the pro-protease may be transferred between yolk granules via v esicular shuttling. B. germanica embryos of different developmental st ages were also exposed to [H-3]-DAMP. Data show that autoradiographic grains are not evenly distributed among closely adjacent yolk granules within vitellophagic cells, a result consistent with the known slight temporal asynchrony of the acidification event.