Identification of a cytochrome P450 CYP6AB60 gene associated with tolerance to multi-plant allelochemicals from a polyphagous caterpillar tobacco cutworm (Spodoptera litura)

Generalist phytophagous insects adapt to adventurous chemical environment in a wide variety of host plants by extraordinary detoxifying metabolic abilities. However, how polyphagous insect cope with the diversity of plant defenses remains largely unknown and only a few counter-defense genes detoxifying a wide range of toxic secondary metabolites have been well characterized. Here, we identify a cytochrome P450 gene (CYP6AB60) from tobacco cutworm (Spodoptera litura) in response to three different plant's defense metabolites. After being exposed to artificial diet supplemented with coumarin (COU), xanthotoxin (XAN) or tomatine (TOM), activities of P450 and CYP6AB60 transcript levels in both midgut and fat body tissues were significantly increased. Developmental expression analysis revealed that CYP6AB60 was expressed highly during the larval stages, and tissue distribution analysis showed that CYP6AB60 was expressed extremely high in the midgut, which correspond to the physiological role of CYP6AB60 from S. litura larvae in response to plant allelochemicals. Furthermore, when larvae are injected with double-stranded RNA (dsRNA) specific to CYP6AB60, levels of this transcript in the midgut and fatbody decrease and the negative effect of plant's defense metabolites on larval growth is magnified. These data demonstrate that the generalist insect S. litura might take advantage of an individual detoxificative gene CYP6AB60 to toxic secondary metabolites from different host plants. The CYP6AB60 can be a potential gene to carry out RNAi-mediated crop protection against the major polyphagous pest S. litura in the future.