WHY ARE THERE SO FEW RESISTANCE-ASSOCIATED MUTATIONS IN INSECTICIDE TARGET GENES

The genes encoding the three major targets of conventional insecticide s are: Rdl, which encodes a gamma-aminobutyric acid receptor subunit ( RDL); para, which encodes a voltage-gated sodium channel (PARA); and A ce, which encodes insect acetylcholinesterase (AChE). Interestingly de spite the complexity of the encoded receptors or enzymes, very few ami no acid residues are replaced in different resistant insects: one with in RDL, two within PARA and three or more within AChE. Here we examine the possible reasons underlying this extreme conservation by looking at the aspects of receptor and/or enzyme function that may constrain r eplacements to such a limited number of residues.