The Carboxylesterase Gene BoαE1 Mediated Detoxification Mechanism of Phoxim in Bradysia odoriphaga

Xie Yuan; Zhang Xiaochen; Xiao Hongli; Li Yaofa; Liu Yingchao; Tang Bowen

doi:10.15933/j.cnki.1004-3268.2026.08.010

Abstract：Bradysia odoriphaga is a major pest of Chinese chive and has developed resistance to the commonly used organophosphorus insecticide phoxim.To elucidate the detoxification mechanism of B.odoriphaga against phoxim,a combination of methods including carboxylesterase-specific inhibitor synergism assay,quantitative real-time PCR,RNA interference(RNAi),and in vitro inhibition assay were employed.The results showed that under exposure to the 30%lethal concentration(LC30)of phoxim,carboxylesterase activity in third-instar larvae increased significantly.The carboxylesterase activities at 12,24,36,and 48 h post-treatment were 40.03,32.91,30.03,and 27.98 μmol/(mg·min),representing 2.44-,1.68-,1.58-,and 1.82-fold increases compared to the blank control.Following treatment with the specific carboxylesterase inhibitor triphenyl phosphate(TPP),the mortality of the larvae reached 41.67%,which was 8.34 percentage points higher(a relative increase of 25.0%)than the control group not fed with TPP.Under phoxim stress,the expression level of the carboxylesterase gene BoαE1 was significantly up-regulated.Knockdown of BoαE1 by RNAi resulted in a corrected mortality rate of 56.25%,representing a 30.44 percentage point increase(a relative increase of 117.9%)compared to the control larvae without gene silencing.In vitro inhibition assays further demonstrated that phoxim inhibited the activity of the recombinant BoαE1 protein with a half-maximal inhibitory concentration(IC50)of 4.020×10-4 mg/L.In conclusion,the carboxylesterase gene BoαE1 is involved in the detoxification metabolism of phoxim in B.odoriphaga and plays a crucial role in the development of resistance to organophosphorus insecticides.