VITELLIN AND FORMATION OF YOLK SPHERES IN VITELLOGENIC FOLLICLES OF THE MOTH, PLODIA-INTERPUNCTELLA

Vitellin (Vt) was found not to be critical to the formation or structu re of yolk spheres in oocytes of the moth, Plodia interpunctella (Hubn er). Vitellogenic activities of the follicular tissues were determined by visualizing the immunocytolocalization of Vt subunits (YP1 and YP3 ) and of a follicular epithelium yolk protein (FEYP) subunit (YP2) in ultrathin sections or in whole-mounted tissues. Vitellogenin was detec table in the inter-follicular epithelial cell (FC) spaces of patent, v itellogenic follicles of normal females. When the follicles entered te rminal growth phase, the inter-FC spaces closed equatorially around th e follicle which excluded vitellogenin from that region. The closure o f the spaces spread towards the poles in more mature follicles. Vt was immuno-localized to yolk spheres of vitellogenic and terminal growth phase oocytes. To examine the role of Vt in formation of yolk spheres, ovaries were transplanted into males. Vt was not detected in the inte r-FC spaces, vitelline membrane, or yolk spheres of follicles from tra nsplanted ovaries developing in males. However, the FEYP subunit YP2 w as detected in the Golgi apparatus and secretory vesicles of columnar FC and in the yolk spheres of the oocytes from transplanted ovaries. D uring the late vitellogenic period, late yolk spheres appeared in the cortical region of the oocytes. In addition, YP2 was detected in the e lectron-translucent vitelline membrane of terminal growth phase follic les. We conclude that Vt is not required for the formation of yolk sph eres or the electron-translucent layer of vitelline membrane. (C) 1995 Wiley-Liss, Inc.