( A team led by biologists at the Univers...)UCSD discovery may help extend life of natural pesticide

Their findings should facilitate the design and use of Bt toxins to prevent insects, which the researchers believe also possess the molecule, from developing resistance to Bt, extending the life of this natural pesticide.

The study, published February 11 in the journal Science, details the structure of a molecule to which Bt attaches, or "binds," in the lining of the intestines of insects and roundworms. The molecule is a glycolipid--a lipid attached to a tree-like arrangement of sugars. Because changes in the sugars impact Bt's ability to bind, the researchers believe that their discovery will make it possible to develop better pesticides and lead to new treatments for parasitic infections that affect close to two billion people worldwide.

"Our previous findings with the roundworm C. elegans strongly suggested that specific sugar structures are likely critical for Bt toxin susceptibility," said Joel Griffitts, the first author on the paper and a former graduate student with UCSD biology professor Raffi Aroian. "This latest paper demonstrates what these sugars actually do. They provide a receptor for the toxin that allows the toxin to recognize its "victim"--a roundworm or an insect. This paper also brings us from the conceptual realm to the chemical nature of these sugar structures--how their atoms are arranged, and how the toxin binds to them."

"Bt toxin, which is produced by a soil bacterium, is toxic to insects and roundworms, but not to vertebrates, which accounts for its popularity as a pesticide," explained Aroian, who led the team. "But the development of insect resistance to Bt is a major threat to its long term use. Our
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Source:University of California - San Diego