Submitted to: Proceedings of the National Academy of Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/6/2008
Publication Date: 4/10/2008
Publication URL: http://handle.nal.usda.gov/10113/62779
Citation: Brown, M.R., Clark, K.D., Gulia, M., Zhao, Z., Garczynski, S.F., Crim, J.W., Suderman, R.J., Strand, M.R. 2008. An insulin-like peptide regulates egg maturation and metabolism in the mosquito aedes aegypti. Proceedings of the National Academy of Sciences, Vol 105(15):5716-5721. Interpretive Summary: To reduce chemical insecticide contamination of the environment, apple and pear growers need non-pesticidal methods to control codling moth, the major insect pest that causes fruit damage. Scientists at the USDA-ARS Yakima Agricultural Laboratory in Wapato, WA in conjunction with Researchers at the University of Georgia are conducting research to find ways to identify targets that prevent egg formation in insect pests, including the codling moth. Insulin-like peptides regulate a variety of critical physiological processes in insects. This manuscript provides up-to-date information on the role of Insulin-like peptides in egg formation in the mosquito, a model system for Insulin signaling. The information in this manuscript will provide scientists the information and technology they need to develop more effective means to regulate egg formation in insect pests, including the codling moth. This line of research will result in the decreased use of chemical insecticides in apple and pear orchards in the Pacific Northwest.
Technical Abstract: Ingestion of vertebrate blood is essential for egg maturation and transmission of disease-causing parasites by female mosquitoes. Prior studies with the yellow fever mosquito, Aedes aegypti, indicated blood feeding stimulates egg production by triggering the release of hormones from MNCs in the mosquito brain. The ability of bovine insulin to stimulate a similar response further suggested this trigger is an endogenous ILP. Ae. aegypti encodes eight predicted ILPs, and we report here that synthetic ILP3 dose-dependently stimulated yolk uptake by oocytes and ecdysteroid production by the ovaries at lower concentrations than bovine insulin. ILP3 also exhibited metabolic activity by elevating carbohydrate and lipid storage. Binding studies using ovary membranes indicated that ILP3 had an IC50 value of 5.9 nM that was poorly competed by bovine insulin. Autoradiography and immunoblotting studies suggested that ILP3 binds the MIR, while loss of function experiments showed that ILP3 activity requires MIR expression. Overall, our results identify ILP3 as a critical regulator of egg production by Ae. aegypti.