Postendocytic vitellin processing in ovarian follicles of the stick insect Carausius morosus (Br.)

Abstract

Newly laid eggs of the stick insect Carausius morosus contain two native vitellins (Vit A and Vit 6). Under denaturing conditions, these vitellins resolved into 3 (AI, A2, and A3) and 2 (61 and B2) polypeptides. All of these polypeptides had counterparts in the female hemolymph from which they were shown to be derived by in vivo labelling. During ovarian development, the 2 vitellins changed both in charge and polypeptide composition. In EV and LV follicles, Vit A resolved into 4 distinct vitellin polypeptides (A@ A1, A2 and A3). Using a panel of monoclonal antibodies, polypeptide p0 proved to be immunologically related to polypeptide A2. In follicles about to begin choriongenesis, polypeptide A3 was gradually replaced by a lower M, polypeptide. Over the same time period, polypeptide B 1 changed in charge, but not in M,. To confirm the existence of a polypeptide processing in C. rnorosus, ovarian follicles of different developmental stages were exposed in vivo to [35S]-methionine from 6 to 72 h. Data showed that A0 and B1 were the polypeptides most heavily labelled after short time exposures to the radioisotope. Polypeptides 62 and A3 were also labelled to some extent. With progressively longer exposures, polypeptides A1 and A2 also became labelled. In vivo exposure to HI-GlcNAc caused all vitellin polypeptides to become heavily labelled. Autoradiographic analysis of ovarian follicles labelled this way showed that, during development, radioactivity was gradually transferred frsm newly formed yolk spheres in the cortical ooplasm to the central ooplasm. Data were interpreted as suggesting a causal relationship between polypeptide processingand progressive yolk sphere fusion to yield the central ooplasm. o 1993 WiIey-Liss, Inc.

Oogenesis and egg development in triatomines: a biochemical approach

“…The decrease in the content of glucose of VT3 must be attributed to the post-endocytic processing of VG. Post-endocytic processing of VT has already been reported by Giorgi et al (1993). The lack of glucose in the oligossacharide associated with VT2 can be attributed to its different origin.…”

Vitellogenesis and Post-Vitellogenic Maturation of the Insect Ovarian Follicle

“…The enzymes include b-N-acetylglucosaminidase in Xenopus (Wall and Meleka, 1985), and serine proteases and cathepsin B and L in Drosophila and Bombyx Medina et al, 1988;Medina and Vallejo, 1989). Giorgi et al (1993b) have suggested that Golgi-derived vesicles deliver hydrolytic enzymes from the Golgi complex to the yolk bodies.…”

An Ultrastructural Investigation on Vitellophage Invasion of the Yolk Mass during and after Germ Band Formation in Embryos of the Stick Insect Carausius morosus Br.

“…Yolk is transferred to the ovarian follicle by a process of endocytosis from the maternal bloodstream (27). Yolk precursors or vitellogenins are high molecular weight lipo-glycoproteins (16) synthesized in the female fat body (26), and extensively modified prior to secretion into the haemolymph (1 8, 19) and endocytosis by the oocyte (9,30). Once in the oocyte, vitellins are partitioned in the yolk granules for long term storage (24).…”