UC-R researcher helps discover mosquito IGRs in plants

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January 27, 2015

Alexander RaikhelRIVERSIDE, CA —As their name suggests, insect growth regulators (IGRs) are compounds that regulate the growth of insects. One hormone in insects, juvenile hormone, is a particularly attractive IGR target because it exists only in insects. Juvenile hormone plays key roles in insect development, reproduction and other physiological functions.

An international team of scientists, including an entomologist at the University of California-Riverside, has investigated in detail how juvenile hormone acts — and has devised a method to prevent its working.

The researchers, led in the United States by Dr. Alexander Raikhel, a distinguished professor of entomology at UC-Riverside, discovered potent compounds in plants that counteract the action of juvenile hormone. These compounds, called juvenile hormone antagonists (JHANs), make up plants’ innate resistance mechanism against insect herbivores.

In collaboration with Korean scientists, Raikhel’s lab screened 1,651 plant species and chose active JHANs from these plants. They then identified five JHANs from two plants that are effective in causing mortality of yellow fever mosquito larvae, specifically by slowing the development of ovaries.

“Our experiments showed that these five JHANs are effective against yellow fever mosquitoes,” Raikhel said. “Our Korean collaborators, led by Sang Woon Shin at Seoul National University, are testing the effect of these five molecules on other agricultural pests. These newly discovered natural molecules could lead to the development of a new class of safe and effective pesticides to control mosquitoes and, we expect, other agricultural pests.”

Study results appear online in the Proceedings of the National Academy of Sciences.

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