Regulation of Vitellogenesis in Insects: The Pleiotropic Role of Juvenile Hormones

Abstract

Endocrine controlled egg production in insects has been a major research topic since Wigglesworth [1] discovered the source of a hormone that promotes vitellogenesis in Rhodnius prolixus. Emphasis has been directed in recent years towards an understanding of the molecular mode of hormone action, and this has been particularly fruitful with regard to juvenile hormone (JH) directed vitellogenin synthesis [2,3]. Vitellogenin is the precursor to the major yolk protein of the mature eggs. It is produced in the fat bodies of most species, but in Drosophila the follicular epithelial cells of the ovaries also produce an identical protein species [4]. JH-controlled vitellogenin synthesis is a dramatic event, both because it is produced in an all-or-none fashion upon JH exposure and because of the massive quantities synthesized within a short period. Hormonal control is basically via induction of transcriptional events which are amenable to an experimental approach in many species of insects, and in analogy, as well in egg-laying vertebrates, such as amphibians and birds.