The symbiont Wolbachia increases resistance to bifenthrin in Ectropis grisescens by regulating the host detoxification function.

The global issue of insecticide resistance among pests is a major concern. Ectropis grisescens Warren (Lepidoptera: Geometridae), is a highly destructive leaf-eating pest distributed in tea plantations throughout China and Japan, and has exhibited resistance to various insecticides. Recent studies suggest that insect symbionts play a role in influencing insecticide resistance, however, their specific involvement in E. grisescens remains unclear. Here, we initially selected appropriate antibiotic mixtures at a concentration of 300 μg ml^-1. The bioassay results showed that the insecticide susceptibility of the E. grisescens population treated with antibiotic mixtures significantly increased exposed to bifenthrin. Comparative analysis revealed that the LC₅₀ value, survival rate, P450 enzyme activity, and relative content of Wolbachia in the E. grisescens population treated with 300 μg ml^-1 tetracycline were notably lower than those treated with other antibiotics (ampicillin, gentamicin, and streptomycin). Moreover, the population treated with 2.5 mg ml^-1 tetracycline exhibited even greater reductions in these parameters than the 300 μg ml^-1 tetracycline-treated group. Additionally, 16S rRNA sequencing results showed a significant decrease in xenobiotics metabolism by cytochrome P450 in the E. grisescens population treated with 2.5 mg ml^-1 tetracycline. Transcriptome analysis showed a significant down-regulation of two cytochrome P450 genes in E. grisescens population without Wolbachia. These results suggest that Wolbachia may contribute to the resistance of E. grisescens to bifenthrin by regulating cytochrome P450 genes, providing a foundation for further study on the mechanism of symbiont-mediated host detoxification metabolism in insect pests.