Suppressing the expression of glutathione S‐transferase gene GSTd10 increases the sensitivity of Zeugodacus cucurbitae against β‐cypermethrin

Zeugodacus cucurbitae Coquillett (Diptera: Tephritidae) is an agriculturally and economically important pest worldwide that has developed resistance to β‐cypermethrin. Glutathione S‐transferases (GSTs) have been reported to be involved in the detoxification of insecticides in insects. We have found that both ZcGSTd6 and ZcGSTd10 were up‐regulated by β‐cypermethrin induction in our previous study, so we aimed to explore their potential relationship with β‐cypermethrin tolerance in this study. The heterologous expression of ZcGSTd6 and ZcGSTd10 in Escherichia coli showed significantly high activities against 1‐chloro‐2,4‐dinitrobenzene (CDNB). The kinetic parameters of ZcGSTd6 and ZcGSTd10 were determined by Lineweaver–Burk. The Vmax and Km of ZcGSTd6 were 0.50 μmol/min·mg and 0.3 mM, respectively. The Vmax and Km of ZcGSTd10 were 1.82 μmol/min·mg and 0.53 mM. The 3D modelling and molecular docking results revealed that β‐cypermethrin exhibited a stronger bounding to the active site SER‐9 of ZcGSTd10. The sensitivity to β‐cypermethrin was significantly increased by 18.73% and 27.21%, respectively, after the knockdown of ZcGSTd6 and ZcGSTd10 by using RNA interference. In addition, the inhibition of CDNB at 50% (IC50) and the inhibition constants (Ki) of β‐cypermethrin against ZcGSTd10 were determined as 0.41 and 0.33 mM, respectively. The Ki and IC50 of β‐cypermethrin against ZcSGTd6 were not analysed. These results suggested that ZcGSTd10 could be an essential regulator involved in the tolerance of Z. cucurbitae to β‐cypermethrin. The 3D modelling and molecular docking results revealed that β‐cypermethrin exhibited a stronger bounding to the active site SER‐9 of ZcGSTd10. The sensitivity to β‐cypermethrin was significantly increased by 27.21% when ZcGSTd10 was suppressed. The IC50 and Ki of β‐cypermethrin against ZcGSTd10 were 0.41 and 0.33 mM, respectively.