Identification of Transcription Factors Regulating Detoxification Genes CYP9Z140, CYP9AY1, and UGT321AP1 Involved in Thiamethoxam Resistance in Leptinotarsa decemlineata

The Colorado potato beetle, Leptinotarsa decemlineata, is a major insect pest of potatoes. Our previous studies have demonstrated that two cytochrome P450 monooxygenase (P450s) genes, CYP9Z140 and CYP9AY1, and a uridine diphosphate–glycosyltransferase (UGT) gene, UGT321AP1, play important roles in thiamethoxam resistance to L. decemlineata. However, the related upstream regulatory mechanism remains unclear. In this study, we first monitored the resistance of L. decemlineata field populations to thiamethoxam in Xinjiang to determine the resistance ratios. The predicted results demonstrated that four transcription factors (TFs), CncC/Maf, Abd-B, FoxO, and Ptx1, may bind to the core regions of three gene promoters. The qRT-PCR results revealed that the TFs were significantly upregulated by thiamethoxam and exhibited specific spatiotemporal expression patterns. Dual-luciferase reporter assays indicated that the CncC pathway could regulate the expression of three detoxification genes, whereas Abd-B and FoxO only regulate CYP9Z140 and UGT321AP1 expressions, respectively. Ptx1 could regulate the expression of both CYP9AY1 and UGT321AP1. Furthermore, knockdown of several TFs through RNA interference significantly reduced expression of the corresponding detoxification genes, consistent with the dual-luciferase reporter assay results, and increased the thiamethoxam susceptibility of test adults. These findings aid in gaining a deeper understanding of the transcriptional regulation mechanisms of insecticide resistance in insects.