Insecticide resistance: A constraint on evolution...( Researchers have identified that a spec...)

Researchers have identified that a specific point in the genetic code appears not only to control an organism's resistance to a class of pesticides but also to significantly influence the ability of an organism to evolve such resistance at all. Identifying such specific and strong constraints on short-term evolutionary change are likely to help ecologists and public-health experts understand, and potentially predict, the ability of particular species to quickly develop resistance to substances such as insecticides. The new work also illuminates the kind of genetic technicality that can shape evolution.

The work, performed by an international team led by Mylene Weill of the Université Montpellier II (France), concerned the ability of mosquito species to develop resistance to two major classes of insecticides, carbamates and organophosphates (OPs). Previous work had shown that a single base-pair alteration, G119S, within the mosquito's version of the AchE1 gene conferred high levels of resistance to these insecticides. Not all mosquito species exposed to high levels of carbamates and OPs develop resistance, however. For example, Anopheles gambiae, the mosquito vector for malaria, is able to develop resistance in this way, whereas Aedes aegytpi, the vector for yellow fever and dengue fever, has never developed high levels of resistance.

The new study reveals the reason for this striking discrepancy in adaptation. First, the researchers determined that the G119S version of the Ae. aegypti AchE1 protein was indeed resistant to insecticide action in the test tube, suggesting that the mutation would confer resistance to the mosquito in principle but that for some reason the mutation does not appear in Ae. aegypti populations. Looking more closely at the Ae. aegypti gene sequence for AchE1 revealed the answer. The researchers found that in this species, the three-letter DNA code at glycine position 119 is di
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Contact: Heidi Hardman
hhardman@cell.com
617-397-2879
Cell Press
26-Jul-2004

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