Glutathione S-transferase TcGSTu1 contributes to defense against eucalyptol in Tribolium castaneum.

Eucalyptol is one of the major insecticidal active ingredients in a variety of plant essential oils, and has good killing and avoidance effects on Tribolium castaneum. The presence of detoxifying enzymes glutathione S-transferase (GST) in T. castaneum makes it resistant to a variety of insecticides. However, whether GST is involved in regulating the sensitivity of eucalyptol by T. castaneum is not well understood. In our previous study, a glutathione S-transferase, TcGSTu1, was significantly up-regulated in RNA sequencing data when T. castaneum was exposed to eucalyptol. Therefore, in this study, the role of TcGSTu1 in the regulating the sensitivity of T. castaneum to eucalyptol was studied. The enzyme activities of GST and the transcription levels of TcGSTu1 were significantly increased following stimulation with eucalyptol. When using RNA interference technology knockdown TcGSTu1 heightens the sensitivity of T. castaneum to eucalyptol, demonstrating a link between TcGSTu1 and eucalyptol detoxification metabolism. Furthermore, TcGSTu1 is expressed in all developmental stages of T. castaneum, with higher expression levels observed particularly in the late egg stage. There was significant expression of TcGSTu1 in various tissues of different organisms, including larval head, fat body, and adult head. This observation indicated a possible connection between high TcGSTu1 expression and eucalyptol detoxification. The present findings suggest that TcGSTu1 may be involved in regulating the sensitivity and response of T. castaneum to treatment with eucalyptol, providing new research insight into pest control.