Insect glutathione S-transferases (GSTs) play a crucial role in the detoxification of exogenous compounds, especially insecticides and plant allelochemicals. A sigma class GST gene, TcGSTS7 , mediates the response to eugenol in Tribolium castaneum . However, the mechanism underlying this effect remains largely unknown. In this study, TcGSTS7 , which exhibits a structural motif and domain organization characteristic of GSTs, was cloned from the T. castaneum genome. Spatiotemporal expression analysis revealed that TcGSTS7 was most highly expressed at the late larva stage and was mainly expressed in the fat body and epidermis of larvae and adults, suggesting that TcGSTS7 may play a potential role in the protection against toxic xenobiotics in T. castaneum . Furthermore, the expression of TcGSTS7 was significantly induced after exposure to eugenol, while RNA interference (RNAi) targeting TcGSTS7 enhanced the sensitivity of the beetle to eugenol, indicating that TcGSTS7 is involved in the tolerance of T. castaneum to this insecticide. Interestingly, the depletion of TcCncC , which encodes a transcription factor of the CncC pathway that has been associated with the regulation of detoxification-related genes in insects, led to a reduction in the TcGSTS7 transcript level following exposure to eugenol, which suggests that TcGSTS7 acts downstream of the CncC pathway. Combined, these results indicated that TcGSTS7 participates in the tolerance of T. castaneum to phytochemicals in a CncC pathway-dependent manner. These findings have implications for the development of novel drugs for use in pest control.
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
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