Esterases A2 and B2 in Culex quinquefasciatus (Diptera: Culicidae): role in organophosphate resistance and linkage

Journal of Medical Entomology
M C WirthN Pasteur

Abstract

Two highly active esterases, A2 and B2, were isolated in SeLax, a strain of Culex quinquefasciatus Say from California which demonstrated resistance levels of 19, 14, and 4.3 times to the organophosphate insecticides chlorpyrifos, temephos, and malathion, respectively. Selection of SeLax by temephos during 31 generations increased resistance to this insecticide to 65 times. This resistance was shown to be DEF-suppressible, monofactorial, and strongly associated with the presence of esterases A2 and B2. Although these two esterases are encoded by distinct structural genes, no disjunction was observed when SeLax was crossed to S-Lab, a susceptible strain, or to S54, a strain resistant to organophosphates by means of esterase A1. However, when SeLax was crossed to strain Tem-R, which is resistant to organophosphates because of a highly active esterase B1, all possible recombinants occurred. These results were discussed in relation to the recent discovery that increased activity of B esterases in the genus Culex is caused by gene amplification.

Citations

Sep 1, 1996·Journal of Molecular Evolution·C RobinJ G Oakeshott
Oct 3, 2001·Journal of Medical Entomology·N PasteurA B Failloux
Nov 30, 2005·Journal of Evolutionary Biology·P LabbeM Raymond
Feb 18, 1999·Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences·M RaymondN Pasteur
Oct 1, 1995·Evolution; International Journal of Organic Evolution·Christine ChevillonMichel Raymond

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