Activation of the ROS/CncC Signaling Pathway Regulates Cytochrome P450 CYP4BQ1 Responsible for (+)-α-Pinene Tolerance in Dendroctonus armandi

Bark beetles mainly rely on detoxification enzymes to resist the host tree’s defense against oleoresin terpenes. Cytochrome P450 enzymes (CYPs) play an important role in the detoxification of plant allelochemicals and pesticides in insect. One P450 gene (DaCYP4BQ1) is associated with the response of (+)-α-pinene inDendroctonus armandi. However, the regulatory mechanism of this P450 gene response to (+)-α-pinene is still unknown. In this study, spatiotemporal expression profiling indicated thatCYP4BQ1was highly expressed in adult and larval stages ofD. armandi, and it was predominantly expressed in fat body, midgut, and Malpighian tubules of adults. Moreover, the expression ofCYP4BQ1significantly increased after exposure to (+)-α-pinene, and depletion of it decreased the tolerance of adults to (+)-α-pinene. In addition, (+)-α-pinene treatment induced the expression of the transcription factors cap ‘n’ collar isoform C (CncC) and its binding factor muscle aponeurosis fibromatosis (Maf), elevated the level of hydrogen peroxide (H2O2), and increased the activities of antioxidant enzymes. SilencingCncCsuppressedCYP4BQ1expression and enhanced the susceptibility of beetles to (+)-α-pinene. Similarly, application of the reactive oxygen species (ROS) scavenger N-acetylcysteine reduced the production and accumulation of H2O2, suppressed the expression ofCncC, Maf, andCYP4BQ1and led to decreased tolerance of adults to (+)-α-pinene. In contrast, ingestion of the CncC agonist curcumin elevatedCYP4BQ1expression and enhanced (+)-α-pinene tolerance. The results demonstrate that, inD. armandi, (+)-α-pinene inducesCYP4BQ1via activation of the ROS/CncC signaling pathway.Keywords:Dendroctonus armandi;phytochemical tolerance;cytochrome P450;oxidative burst;CncC pathway