A high number of mutations in insect acetylcholinesterase may provide insecticide resistance

Many insect pest species have developed insecticide resistance through modi fications of acetylcholinesterase. Seven mutations, issued From one nucleot ide change, have been associated with resistance in natural populations of Drosophila and housefly (A. Mutero, M. Pralavorio, J. M. Bride, and D. Four nier, Resistance-associated point mutations in insecticide insensitive acet ylcholinrsterase, Proc Nail. Acad Sci. USA 91, 5922 (1994); A. L. Drvonshir e, F. J Byrne, G, D. Moores, and M. S. Williamson, Biochemical and molecula r characterisation of insecticide-insensitive acetylcholinesterases in resi stant insects, in "Structure and function of cholinesterases and related pr oteins" (B. P. Doctor, P. Taylor, D. M. Quinn, R. L. Rotundo, and M. K. Gen try, Eds.), DD. 491-496, Plenum Press, New York, 1998). In order to study t he number of mutations which can lead to resistance, we first analyzed the effects of a set of amino acid replacements in the Drosophila acetylcholine sterase on inhibition by several carbamate and organophosphate insecticides . It appeared that most of the mutations led to a reduced sensitivity to in secticides. Second, we investigated the effect of mutations on substrate hy drolysis. We found that most of the variants retained sufficient levels of substrate hydrolysis. These data suggest that more mutations in acetylcholi nesterase may be involved in organophosphate and carbamate resistance in ad dition to the previously known seven mutations. (C) 2000 Academic Press.