Nubbin-Regulated UDP-Glycosyltransferase NlUGT386G5 Mediates Quercetin Detoxification in the Brown Planthopper Nilaparvata Lugens

Quercetin is a defensive flavonoid that accumulates in rice following infestation by the brown planthopper (BPH), Nilaparvata lugens, but how BPH detoxifies quercetin remains unclear. Dietary quercetin reduced female survival and body weight in a dose-dependent manner. Transcriptomic analysis identified NlUGT386G5, which encodes a UDP-glycosyltransferase, as a quercetin-responsive candidate detoxification gene. Silencing NlUGT386G5 markedly increased BPH susceptibility to quercetin. Molecular docking and molecular dynamics simulations supported stable binding of quercetin to the NlUGT386G5 protein. Recombinant enzyme assays and LC-MS/MS showed that recombinant NlUGT386G5 converted quercetin into quercetin-3-O-glucoside, which did not significantly affect BPH survival or body weight. Promoter analysis and dual-luciferase assays identified the POU-domain transcription factor NlNubbin as a positive regulator of NlUGT386G5 transcription; NlNubbin knockdown reduced quercetin-induced NlUGT386G5 expression and tolerance to quercetin. Together, these results establish the NlNubbin-NlUGT386G5 pathway as a regulatory mechanism underlying quercetin detoxification and tolerance in BPH.