COMPARATIVE NEUROENDOCRINE CONTROL OF REPRODUCTION IN MOTHS

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During copulation, Heliothis virescens males transfer juvenile hormone (JH) to females and stimulate biosynthesis and release of her endogenous JH, while inhibiting JH degradation, thus stimulating egg maturation. This effect is hypothesized to be mediated via the brain, involving continued release of allatotropins that stimulates JH production by mated female corpora allata (CA) and simultaneously release of a JH-esterase inhibitor. Our ability to determine in vivo JH titers using gas chromatography-mass spectrometry and to measure in vitro JH biosynthesis and release by CA, combined with explicit physiological experiments show allow a determination of mechanisms involved in the mating-induced egg production seen in H. virescens. Heliothis virescens moths are readily available and easily reared in the laboratory. Numerous studies on the reproductive biology of this species suggest they are similar to other leptidopterans in many aspects of their reproductive physiology and, thus, serve as an excellent model to study these processes in Lepidoptera. The focus of this proposal is to study dynamics of JH titers in female Heliothis virescens, with the hypothesis that levels of endogenous JH decline with age in the virgin female and that on mating she derives a male factor that affects her brain, with a concomitant allatotropic and gonadotropic effect. The specific objectives of the proposed research to test this hypothesis are to: 1) determine the role of the female's brain- subesophageal ganglion (brain-SEG) complex in post-mating stimulation of egg production; 2) measure response of CA from mated and virgin female brain-SEG; and 4) sequence the H. virescens allatotropin. Results from experiments proposed, combined with data from concurrent studies on the nature of allatotropin/allatostatin in H. virescens, should provide a definitive explanation of the physiology of mating-induced gonadotropism in Lepidoptera, and also increase our knowledge of the interactions between neuropeptides and other endocrine secretions in the integrative physiology of animals. This project will be implemented in close collaboration with Dr. S.B. Ramaswamy, Chair and Professor, Department of Entomology, Kansas State University, who has also agreed to allow the investigator the use of his laboratory facilities.