Overexpression of Two Odorant Binding Proteins Confers Chlorpyrifos Resistance in the Green Peach Aphid <i>Myzus persicae</i>

The green peach aphid, <i>Myzus persicae</i>, is a worldwide agricultural pest. Chlorpyrifos has been widely used to control <i>M. persicae</i> for decades, thus leading to a high resistance to chlorpyrifos. Recent studies have found that insect odorant binding proteins (OBPs) play essential roles in insecticide resistance. However, the potential resistance mechanism underlying the cross-link between aphid OBPs and chlorpyrifos remains unclear. In this study, two OBPs (MperOBP3 and MperOBP7) were found overexpressed in <i>M. persicae</i> chlorpyrifos-resistant strains (CRR) compared to chlorpyrifos-sensitive strains (CSS); furthermore, chlorpyrifos can significantly induce the expression of both OBPs. An <i>in vitro</i> binding assay indicated that both OBPs strongly bind with chlorpyrifos; an <i>in vivo</i> RNAi and toxicity bioassay confirmed silencing either of the two OBPs can increase the susceptibility of aphids to chlorpyrifos, suggesting that overexpression of MperOBP3 and MperOBP7 contributes to the development of resistance of <i>M. persicae</i> to chlorpyrifos. Our findings provide novel insights into insect OBPs-mediated resistance mechanisms.