STRUCTURE AND ORGANIZATION OF AMPLICONS CONTAINING THE E4 ESTERASE GENES RESPONSIBLE FOR INSECTICIDE RESISTANCE IN THE APHID MYZUS-PERSICAE(SULZER)

Insecticide resistance in the aphid Myzus persicae results primarily f rom the amplification of genes encoding the insecticide-detoxifying es terase, E4. Here we report the analysis of flanking DNA co-amplified w ith the E4 gene. The 5' end of this gene has an untranslated leader se quence interspersed by two introns, and the promoter region lacks TATA and CAAT boxes. The DNA breakpoint involved in the generation of the amplification is just upstream (approx. 250 bp) of the putative E4 tra nscription start site; thus the E4 gene is very close to the 5' end of the approx. 24 kb amplicon. PCR primers specific to the 'novel joint' generated during the amplification have been used to show that a wide range of aphid clones have the same amplicons, arranged as a series o f head-to-tail direct repeats. Long-distance mapping has revealed the structure of these repeats. This has important implications for unders tanding both the generation of the amplified genes and the origin and spread of insecticide resistance in M. persicae.