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Title: ACTION CASCADE OF AN INSECT GONADOTROPIN, TESTIS ECDYSIOTROPIN, IN MALE LEPIDOPTERA

Author
item Loeb, Marcia
item Bell, Robert
item Gelman, Dale
item Kochansky, Jan
item LUSBY, WILLIAM - USDA, ARS, RETIRED
item Wagner, Renee

Submitted to: Invertebrate Reproduction and Development
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/30/1995
Publication Date: N/A
Citation: N/A

Interpretive Summary: This paper is a review of our work on the mechanism by which the reproductive system of male tobacco budworm and gypsy moth is controlled by the hormones of these animals. These pest insects destroy a large part of the cotton crop and hardwood forests, respectively, in the U. S. and the rest of the world, and, therefore, are economically extremely important. It would be of great advantage to curtail the reproductive potential of these pest species. However, in order to accomplish this effectively, it is important to understand how the reproductive systems function. This work makes an effort to organize the available knowledge of male reproductive physiology for these organisms. The information will be used primarily by other scientists.

Technical Abstract: Testis sheaths from late last instar larvae and mid-developing pupae of Heliothis virescens and Lymantria dispar synthesize ecdysteroid in vitro. Gonadal ecdysteroid can stimulate the production of growth factors from the sheaths which, in turn, promote the growth and development of the genital tract. Ongoing basal synthesis is controlled by positive feedback to exogenous ecdysteroid; titers of this hormone approaching those of molting last instar larvae and developing pupae effect maximum synthesis. These findings suggest that circulating titers of ecdysteroid hormone promote gonadal ecdysteroidogenesis, and thus coordinate the actions of the gonads with metamorphic events in the whole animal. Synthesis of ecdysteroid by testes is initiated, however, by a brain neuropeptide, testis ecdysiotropin (TE). TE is a 21 amino acid peptide of molecular weight 2472 Da. TE boosts basal steroid synthesis by pupal testis sheaths as well. It acts primarily via Gi protein and second messengers diacyl glycerol and low calcium influx, resulting in stimulation of phosphokinase C. Gs protein and its resultant messenger, cyclic AMP, also play roles in activation and inhibition of ecdysteroidogenesis. The interplay of controlling systems probably serves to fine tune a system essential to gonadal development and function.