This research is on characterizing the key intermediates in the functioning of juvenile hormones (JH) in insect development and will be supported by the Organic and Macromolecular Chemistry Program. This research will lead to the elucidation of JH action which will provide insights into alternative methods of insect control. Unknown endogenous juvenoids and anti-juvenoids in insects will be isolated and characterized by the use of receptor binding assays to guide fractionation, purification, and authenication. These invertebrate compounds may be morphogens or anti-morphogens involved in receptor protein-mediated transcription of chromosomal DNA. 1. Endogenous Juvenoids. Juvenile hormone (JH) action can be mimicked in vivo by over five thousand synthetic juvenoids, many unrelated to JH itself. Tritium and I-125 labeled JH mimics developed at SUNY, Stony Brook were used to discover the existence of unique juvenoid binding sites in target cell nuclei of the tobacco hornworm. These sites do not recognize JH homologs. Thus it is predicted that endogenous small molecules are present in immature insects which are natural ligands for these juvenoid receptors. Using the binding of tritium-methoprene or tritium-S-31183 (or their photolabile analogs), the competitive binding materials will be purified from early instar Manduca (tobacco hornworm) larvae to establish the existence and structure of these natural morphogens. 2. Inhibitors of Termite Caste Differentiation. Soldier termites produce abundant defense secretions in their head; in addition, it has now been found that other substances are present, which can inhibit the methoprene-induced molting of workers into presoldiers. Termite workers and larvae of the Eastern subterranean termite Reticulitermes flavipes are an abundant resource for isolation of methoprene receptor involved in stimulating caste differentiation, while soldiers and nymphs contain inhibitory pheromones which block this action of methoprene in vivo. An in vitro biochemical assay has been developed by which changes in hemolymph JH binding proteins induced by methoprene are detected by photoaffinity labeling.
