Xenobiotic detoxification in the navel orangeworm Amyelois transitella (Lepidoptera: Pyralidae)

The highly polyphagous navel orangeworm, Amyelois transitella, is a major pest of high-value tree crops such as pistachios and almonds. These non-native crops have been grown commercially in the United States for less than 150 years, and the acquisition by the navel orangeworm of these and other novel hosts may have been facilitated by its metabolic capacity to detoxify xenobiotics. Using Illumina RNA sequencing, I characterized the cytochrome P450 genes transcribed in the midgut of the caterpillar. A total of 319 million paired-end reads were sequenced from larval midgut tissue, and these were assembled de novo into 186,000 contigs. Identification of putative P450s in this assembly was carried out using BLAST homology. As detoxification of phytochemicals, mycotoxins, and pesticides is mediated at least in part by P540 enzymes, developing genomic resources for characterizing P450s and elucidating their function in this insect will aid in management efforts for this pest. An important component of elucidating P450-mediated detoxification in this highly polyphagous species is to understand how ingestion of multiple types of toxins influences detoxification. One pyrethroid pesticide used in almond orchards, α-cypermethrin, is likely detoxified by P450 genes transcribed in the navel orangeworm midgut. Dietary exposure to two phytochemicals found in almonds and pistachios, chlorogenic acid and quercetin, increases survival of navel orangeworms exposed to α-cypermethrin. These phytochemicals may decrease toxicity of the pesticide by inducing the P450s involved in its detoxification. Decreased effectiveness of α-cypermethrin is a concern to almond and pistachio growers. Characterization of the P450s involved in pesticide detoxification in the navel orangeworm on its multiple host plants can inform pesticide management strategies for this pest