Photoaffinity labeling of juvenile hormone epoxide hydrolase and JH-binding proteins during ovarian and egg development in Manduca sexta

Abstract

Developmental profiles of a membrane-associated 50 kDa juvenile hormone epoxide hydrolase (JHEH) and a cytosolic 32 kDa juvenile hormone binding protein (JHBP) in the ovaries and eggs of Manduca sexta were obtained using photoaffinity analogs of JHs. The 50 kDa JHEH was present at a constant level in adult female ovaries, in eggs, and in first instar larvae. In contrast, the cytosolic 32 kDa JHBP was absent in pupae and increased significantly in the adult. The cytosolic 32 kDa JHBP in eggs had properties similar to the hemolymph 32 kDa JHBP in terms of size, isoelectric point, ligand specificity, and immunoreactivity. The level of hemolymph 32 kDa JHBP, however, was present throughout pupal and adult stages. The JH-specific esterase (JHE) activity in ovaries also increased in the adult, remained unchanged until oviposition, and decreased in eggs between days 1 and 2 after oviposition. These results show an increase of cytosolic JHBP and JHE at the termination phase of vitellogenesis and oogenesis. Moreover, it appears that high JHE and JHEH activity in the embryo helps maintain a sufficiently low JH titer to circumvent inhibition of embryonic development. Finally, a hemolymph 80 kDa protein, which was present in larvae and pupae but was absent in the newly eclosed adult female, was also specifically labeled by the JH photoaffinity analogs.