Abstract
Beet armyworm, Spodoptera exigua (Hübner) is an agronomical important and most devastating polyphagous pest that damages a variety of crops around the globe including China. Quercetin is one of the abundant dietary flavonoids and the important defense allelochemicals in plants. Therefore, the changes in insect detoxification enzymes activities in response to plants allelochemicals may result increased the sensitivity to insecticides. In this study, we examined the induced effect of quercetin on larval tolerance to lambda-cyhalothrin in S. exigua. Application of cytochrome P450 inhibitor piperonyl butoxide (PBO) significantly synergized the lambda-cyhalothrin toxicity in quercetin-fed S. exigua larvae. Moreover, larval weight significantly reduced in quercetin, lambda-cyhalothrin, and quercetin + lambda-cyhalothrin treatment. Furthermore, our results showed that the P450 detoxification enzyme effectively increased in all treatments as compared to the control. Quantitative Real-time PCR analysis revealed that expression level of CYP6AE10 significantly upregulated in larvae treated with quercetin, lambda-cyhalothrin and quercetin + lambda-cyhalothrin in the midgut and fat body respectively. In addition, RNAi mediated knockdown of CYP6AE10 in S. exigua larvae significantly decreased the transcription level of target cytochrome P450 gene followed by the exposure with quercetin, lambda-cyhalothrin, and quercetin + lambda-cyhalothrin. Similarly, the knockdown of CYP6AE10 by the injection of dsRNA led to increased mortality after the treatment with respective chemicals. Overall, these data showed that P450s might possibly play an important role in the metabolic adaptation of S. exigua larvae to its host plant defense allelochemicals as well as insecticides. In conclusion, S. exigua can take benefit from its host plant’s secondary metabolites to elaborate its defense against synthetic insecticides.