Biochemical evidence that an S431F mutation in acetylcholinesterase-1 of Aphis gossypii mediates resistance to pirimicarb and omethoate

Molecular changes in acetylcholinesterase (AChE) leading to target-site resistance to carbamate and organophosphate insecticides have recently been identified. Of particular interest is the S431F mutation in ace2 and its orthologue ace1 of Myzus persicae Sulzer and Aphis gossypii Glover, respectively. This mutation has been correlated with resistance to pirimicarb, but biochemical evidence has not yet been provided. Here, we describe for the first time that recombinantly expressed AChE1 from A gossypii carrying the S431F mutation is insensitive to pirimicarb and omethoate, but sensitive to demeton-S-methyl and hypersensitive to carbofuran. Furthermore, site-directed mutagenesis of the serine residue at position 431 in ace1 from a pirimicarb-susceptible clone of A gossypii conferred insensitivity to pirimicarb. We conclude that AChE1 of A gossypii is the target of toxicological relevance of carbamates and organophosphates. (C) 2004 Society of Chemical Industry.