Amplification of a Cytochrome P450 Gene Is Associated with Resistance to Neonicotinoid Insecticides in the Aphid Myzus persicae

Abstract

The aphid Myzus persicae is a globally significant crop pest that has evolved high levels of resistance to almost all classes of insecticide. To date, the neonicotinoids, an economically important class of insecticides that target nicotinic acetylcholine receptors (nAChRs), have remained an effective control measure; however, recent reports of resistance in M. persicae represent a threat to the long-term efficacy of this chemical class. In this study, the mechanisms underlying resistance to the neonicotinoid insecticides were investigated using biological, biochemical, and genomic approaches. Bioassays on a resistant M. persicae clone (5191A) suggested that P450-mediated detoxification plays a primary role in resistance, although additional mechanism(s) may also contribute. Microarray analysis, using an array populated with probes corresponding to all known detoxification genes in M. persicae, revealed constitutive over-expression (22-fold) of a single P450 gene (CYP6CY3); and quantitative PCR showed that the over-expression is due, at least in part, to gene amplification. This is the first report of a P450 gene amplification event associated with insecticide resistance in an agriculturally important insect pest. The microarray analysis also showed over-expression of several gene sequences that encode cuticular proteins (2–16-fold), and artificial feeding assays and in vivo penetration assays using radiolabeled insecticide provided direct evidence of a role for reduced cuticular penetration in neonicotinoid resistance. Conversely, receptor radioligand binding studies and nucleotide sequencing of nAChR subunit genes suggest that target-site changes are unlikely to contribute to resistance to neonicotinoid insecticides in M. persicae.

A cis-regulatory sequence driving metabolic insecticide resistance in mosquitoes: Functional characterisation and signatures of selection

“…Whilst CYP9M10 can be induced by recent exposure (Liu et al, 2011) this cannot explain the levels estimated by Hardstone et al (2010) which are much higher even than for tandemly duplicated genes e.g. esterase E4 in aphids which exhibit fold changes of >60 (Puinean et al, 2010). Nevertheless, the over-expression encountered in our study is compatible with gene expression underlying the observed phenotype.…”

Identification and validation of a gene causing cross-resistance between insecticide classes inAnopheles gambiaefrom Ghana

“…Qualitatively higher CYP6M2 expression was recorded in the DDT-resistant group, 2.36-fold greater expression compared with Akron and 1.54-fold compared with the Ngoussou colony, although these values were less than half those observed in the microarray experiment (6.11-fold and 3.67-fold, respectively). This less-than-perfect concordance between qPCR and microarray datasets is a common finding in insect transcriptome studies (15,21,22), and possibly results from the low fold-change (23) or absolute levels of expression.…”

The Molecular Genetics of Insecticide Resistance

“…Similarly, following control failures with endosulfan in peach orchards in Washington state, M. persicae was also shown to carry point mutations in their Rdl-encoded GABA-gated chloride channels that confer resistance to cyclodienes and endosulfan (Anthony et al 1998). In an unexpected twist, gene duplication was also shown to be correlated with overproduction of a cytochrome P450 (Puinean et al 2010), suggesting that duplication not only was confined to esterases but also could potentially be responsible for the overproduction of other detoxifying enzymes. Finally and most recently, resistance to the novel class of insecticides, the neonicotinoids, has been shown to be associated with a point mutation in the b1-subunit of the Myzus nicotinic acetylcholine receptor (Bass et al 2011).…”