In most insect species examined, juvenile hormone (JH) regulates production of vitellogenin (Vg, egg-yolk protein) by the adult female fat body. Regulation involves new transcription of the Vg gene; however, little evidence is available regarding the mechanism through which this structurally unusual hormone acts. This study proposes to use (1) two-dimensional electrophoresis of proteins, (2) organ culture, and (3) fat body transplants to analyze the primary responses of fat body to JH and to examine the basis for the stage- and sex-specificity of the response. In the house cricket, a nine-hour lag occurs between administration of exogenous JH and initiation of Vg production. Characterization of the cellular events occurring in this induction period should reveal the mechanism involved in activation of the Vg gene. One objective of the proposed study is to analyze the induction period for JH-dependent synthesis of proteins which as primary products of hormone action could, in turn, play a role in regulating the Vg gene. In vivo analyses suggest that cricket fat body should provide a suitable target for the first successful in vitro demonstration of primary induction of the Vg gene by JH, since exogenous JH acts independently of mating, adult feeding, or the presence of known neuroendocrine centers. Thus, a second goal of this research is to establish for cricket fat body appropriate culture conditions for in vitro analysis of JH's inductive mechanism. Juvenile hormone controls numerous aspects of insect growth and development in males and females, and the basis for the sex- and stage-specificity of Vg production by the fat body is not clear. This study will approach the problem through the transplantation of fat body between males and females at various stages of competency. Through these three goals, this research project addresses the question of the control of developmentally specific patterns of gene expression. Although the research model is the induction by juvenile hormone of egg-yolk production in insect fat body, it is expected that the results will provide insight into regulatory mechanisms operative generally in eucaryotic developmental phenomena ranging from embryogenesis to aging.
