Submitted to: Regulatory Peptides
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 20, 1997
Publication Date: N/A
Interpretive Summary: Much study has been done on a class of insect hormones called neuropeptides. Neuropeptides regulate virtually all aspects of insect physiology and are attractive targets for development of new methods of insect pest control. However, neuropeptides do not penetrate the surface of the insect. Therefore, development of new strategies for pest control based on these neuropeptides requires the development of a delivery system that allows these hormones to enter the body after being applied to the surface of the insect. Scientists at the Center for Medical, Agricultural and Veterinary Entomology, USDA, ARS, Gainesville, Florida and Food Animal Protection Research Laboratory, College Station, Texas have synthesized three modified insect neuropeptides that penetrate the insect cuticle and stimulate sex pheromone production for long periods of up to 20 hours. The results provide important information for development of new strategies for pest control based on the use of insect neuropeptides. Additionally, the results provide important information that could be used to design neuropeptides that are important to physiological functions of other organisms, including livestock and humans.
Technical Abstract: Amphiphilic pseudopeptide analogs of Phe-Thr-Pro-Arg-Leu-NH2, representing the active C-terminal core pentapeptide of the pyrokinin class of insect neuropeptides, were synthesized by replacement of phenylalanine with hydrocinnamic acid (Hca-Thr-Pro-Arg-Leu-NH2), or addition of 1-pyrenebutyric acid (Pba-Phe-Thr-Pro-Arg-Leu-NH2) or 9- fluoreneacetic acid (Fla-Phe-Thr-Pro-Arg-Leu-NH2). The pseudopeptides were found to stimulate sex pheromone biosynthesis when injected into females of the moth Heliothis virescens. Optimal pheromonotropic responses were obtained by injection of 0.25 pmol of Hca-Thr-Pro-Arg- Leu-NH2, 2.5 pmol of Pba-Thr-Pro-Arg-Leu-NH2 and 0.5 pmol of Fla-Thr- Pro-Arg-Leu-NH2. Topical application of each of the pseudopeptides in water to the cuticle of moths stimulated significant production of pheromone at a dose of 50 pmol with optimal stimulation occurring when 500 pmol were applied. The parent peptide, Phe-Thr-Pro-Arg-Leu-NH2, failed to stimulate significant production of pheromone when applied topically at a dose as high as 2000 pmol. Temporal studies indicated that Hca-Thr-Pro-Arg-Leu-NH2 stimulated significant production of pheromone for only 4h after application where as continuous pheromone production for 18h was observed when either Pba-Phe-Thr-Pro-Arg-Leu- NH2 or Fla-Phe-Thr-Pro-Arg-Leu-NH2 were applied to the abdomen. The results show that modification of the C-terminal active core of the insect pyrokinins, by addition of hydrophobic moieties, can result in production of pseudopeptides which effectively penetrate the insect cuticle and have prolonged physiological effects making them favorable candidates for use in development of alternative strategies for pest insect control.