A new amino-acid substitution in acetylcholinesterase 1 confers insecticide resistance to Culex pipiens mosquitoes from Cyprus |
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Authors: | Alout Haoues Berthomieu Arnaud Hadjivassilis Andreas Weill Mylène |
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Affiliation: | Laboratoire Génétique et Environnement Institut des Sciences de l'Evolution (UMR CNRS 5554), Université de Montpellier II (C.C. 065), F-34095 Montpellier cedex 05, France. |
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Abstract: | In insects, selection of insecticide-insensitive acetylcholinesterase (AChE) is a very common resistance mechanism. Mosquitoes possess both AChE1 and AChE2 enzymes and insensitivity is conferred by single amino-acid changes located near the active site of the synaptic AChE1. Only two positions have been reported so far to be involved in resistance, suggesting a very high structural constraint of the AChE1 enzyme. In particular, the G119S substitution was selected in several mosquitoes' species and is now largely spread worldwide. Yet, a different type of AChE1 insensitivity was described 10 years ago in a Culex pipiens population collected in Cyprus in 1987 and fixed thereafter as the ACE-R strain. We report here the complete amino-acid sequence of the ACE-R AChE1 and show that resistance is associated with a single Phe-to-Val substitution of residue 290, which also lines the active site. Comparison of AChE1 activities of the recombinant F290V protein and ACE-R mosquito extracts confirmed the causal role of the substitution in insensitivity. Biochemical characteristics of the mutated protein indicated that the resistance level varies with the insecticide used. A molecular diagnosis test was designed to detect this mutation and was used to show that it is still present in Cyprus Island. |
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