Esterase Genes Conferring Insecticide Resistance in Aphids

The amplified esterase genes responsible for insecticide resistance in the aphid Myzus persicae were remarkably conserved in standard laboratory clones and in samples collected from field populations throughout the UK during 1990. Only two restriction patterns were found, each associated with the presence of a different amplified esterase (E4 or FE4). The E4 and FE4 DNA sequences in the field aphids contained 5-methylcytosine (5 mC) at the same sites as in standard clones and although there were no examples of complete loss of methylation and esterase gene transcription, as previously found in revertant clones, there was evidence for partial loss of 5 mC and expression. An apparently identical esterase gene amplification and elevated enzyme (FE4) were found in a resistant Greek population of a closely related species, Myzus nicotianae .