UCR: Each year millions of deaths result from diseases transmitted by
insects. Insects are also responsible for major economic losses, worth
billions of dollars annually, by damaging crops and stored agricultural
products. Many currently available insecticides present environmental and
health risks. Further, insects develop resistance to existing
insecticides, complicating pest-control strategies. The need to develop
novel effective insecticides is therefore urgent.
Enter “insect-specific growth regulators,” which, as their name
suggests, are compounds that regulate the growth of insects. They
represent attractive pest-control agents because they pose no health
risk to humans and are also environmentally safe.
One hormone in insects, called juvenile hormone, is a particularly
attractive target for insect growth regulators because this hormone
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 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 retarding 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 this week in the Proceedings of the National Academy of Sciences.
At UCR, Raikhel’s lab specializes in understanding the molecular
basis of events in the mosquito reproduction cycle linked to a blood
meal and pathogen transmission. His research focuses, too, on how
pathogens of major human diseases, transmitted by mosquitoes, interact
with their mosquito hosts. A member of the National Academy of Sciences, he occupies the Mir S. Mulla Chair in Entomology at UCR, as well as the University of California President’s Chair.
He and Shin were joined in the study by Seok-Hee Lee, Ying Fang,
Saes-Byeol An, and Yeon Ho Je at Seoul National University, Korea;
Hyun-Woo Oh, Doo-Sang Park, Hyun-Hwan Song and Sei-Ryang Oh at Korea
Research Institute of Bioscience and Biotechnology; Soo-Young Kim at the
National Institute of Biological Resources, Korea; and Seonghyun Kim
and Namjung Kim at the National Academy of Agricultural Science, Korea.
Raikhel’s lab was supported in the research by a grant from the National Institutes of Health.