NATIVE VITELLINS ARE MODIFIED DURING OVARIAN DEVELOPMENT IN THE STICKINSECT CARAUSIUS-MOROSUS (BR.)

Vitellins from ovarian follicles and newly laid eggs of the stick inse ct Carausius morosus were examined by ion exchange chromatography on a HPLC Mono Q column. Under these conditions, vitellins from newly laid eggs resolved as two distinct peaks, referred to as VtA and VtB, that eluted at 8.5 and 12.0 min, respectively. On native gels, both VtA an d VtB separated into two different variant forms (VtA' and VtA '', VtB ' and VtB ''). By two-dimensional gel electrophoresis, VtA' and VtA '' were shown to contain polypeptides A(1), A(2) and A(3). On the other hand, VtB' and VtB '' appeared to comprise polypeptides B-1 and B-2 an d B-1, A(1), A(2), B-2 and A(3), respectively. A similar Vt polypepti de composition was also observed by size-exclusion chromatography of v itellins from newly laid eggs. Vitellins from early vitellogenic ovari an follicles resolved into a single chromatographic peak at 7.5 min th at coeluted with a major peak from the hemolymph of egg-laying females . Ovarian follicles progressively more advanced in development exhibit ed a more complex chromatographic profile, consisting of three separat e peaks. By two-dimensional gel immunoelectrophoresis, vitellins from ovarian follicles appeared to consist of two closely related, immunolo gically cross-reacting antigens that gradually shifted apart as ovaria n development proceeded to completion. By size-exclusion chromatograph y, each Vt from ovarian follicles was shown to consist of a unique set of polypeptides different from those listed above. Single ovarian fol licles were fractionated into yolk granules and yolk fluid ooplasm and tested by immunoblotting against Mab 12. Under these conditions, VtA variant forms in yolk granules and yolk fluid ooplasm reacted differen tly. Sections from ovarian follicles in different developmental stages were exposed to Mab 12 and stained with a peroxidase-conjugated, goat anti-mouse antibody. Regardless of the developmental stage attained, staining for peroxidase was restricted to free yolk granules, suggesti ng that native vitellins in stick insects are structurally modified up on fusion into the yolk fluid ooplasm. (C) 1997 Wiley-Liss, Inc.