Submitted to: Archives of Insect Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/23/2000
Publication Date: N/A
Citation: N/A Interpretive Summary: Molting hormone is an exceptionally important hormone because it not only controls insect molting, but also a myriad of other insect processes including egg and sperm production,development of tissues and organs in the embryo, larva, pupa and adult, cuticle production and adult emergence. The regulation of molting hormone production is complex and has been shown to depend on several other hormones and factors as well as on stimulation/inhibition by the nervous system. Biologically-based insect control strategies which interfere with insect growth and development by upsetting the delicate balance of hormones are in great demand. Thus, we undertook to investigate the ability of a small protein-like molecule to inhibit the production of molting hormone. This molecule known as TMOF has been shown to inhibit the production of a digestive enzyme in mosquitoes and flies, and to inhibit the production of molting hormone in flies. Our results show that TMOF modulates the production of molting hormone by gyps moth glands and suggests the presence of a new regulatory molecule in the gypsy moth, which if isolated, could be useful as a biopesticide. The TMOF gene has been shown to be active after it has been genetically engineered into a virus that attacks the tobacco plant, but is harmless to other living organisms. This is the first report of a modulator that can inhibit the production of molting hormone in a lepidopteran pest insect. Such a molecule could eventually be used as a biologically-based control agent to reduce insect populations with minimum harm to the environment, i.e., contamination of ground water, destruction of natural enemies and development of resistance in pest species.
Technical Abstract: Trypsin Modulating Oostatic Factor (TMOF) is a decapeptide which inhibits the biosynthesis of trypsin-like enzymes in the midgut of several insect species. Originally reported to serve as a dipteran oostatic hormone, more recently, it also has been found to inhibit ecdysteroid synthesis by dipteran ring glands. In vitro incubation of lepidopteran prothoracic glands with Aedes aegypti TMOF revealed that this decapeptide, in the presence of brain extract, modulates ecdysteroid production. The modulatory effect was highly dependent on both the concentration of TMOF and of brain extract. Typically, TMOF was stimulatory in the presence of lower concentrations of L. dispar brain extract (0.025 brain equivalent), and either neutral or inhibitory at higher extract concentrations (0.25 and 0.5 brain equivalent). In the presence of European corn borer (Ostrinia nubilalis) brain extract, TMOF exhibited similar modulatory effects. At 1.5 brain equivalents, TMOF was inhibitory at all but the highest concentration tested (5 x 10(-6)M), and at 1.0 brain equivalent, TMOF was stimulatory at 10(-6) M. Results suggest the presence of a modulatory peptide(s) which fine tunes the synthesis and release of ecdysteroids by PTGs in accordance with the insect's developmental/physiological requirements.