Odorant Binding Protein Expressed in Legs Enhances Malathion Tolerance in <i>Bactrocera dorsalis</i> (Hendel)

Abstract

<i>Bactrocera dorsalis</i> is a highly invasive species and is one of the most destructive agricultural pests worldwide. Organophosphorus insecticides have been widely and chronically used to control it, leading to the escalating development of resistance. Recently, odorant binding proteins (OBPs) have been found to play a role in reducing insecticide susceptibility. In this study, we used RT-qPCR to measure the expression levels of four highly expressed OBP genes in the legs of <i>B. dorsalis</i> at different developmental stages and observed the effect of malathion exposure on their expression patterns. The results showed that <i>OBP28a-2</i> had a high expression level in 5 day old adults of <i>B. dorsalis</i>, and its expression increased after exposure to malathion. By CRISPR/Cas9 mutagenesis, we generated <i>OBP28a-2</i>^<i>-/-</i> null mutants and found that they were more susceptible to malathion than wild-type adults. Furthermore, <i>in vitro</i> direct affinity assays confirmed that OBP28a-2 has a strong affinity for malathion, suggesting that it plays a role in reducing the susceptibility of <i>B. dorsalis</i> to malathion. Our findings enriched our understanding of the function of OBPs. The results highlighted the potential role of OBPs as buffering proteins that help insects survive exposure to insecticides.