Identification, Expression, and Regulation of an Omega Class Glutathione S-transferase in Rhopalosiphum padi (L.) (Hemiptera: Aphididae) Under Insecticide Stress

Abstract

Glutathione S-transferases (GSTs) play an essential role in the detoxification of xenobiotic toxins in insects, including insecticides. However, few data are available for the bird cherry-oat aphid, <i>Rhopalosiphum padi</i> (L.). In this study, we cloned and sequenced the full-length cDNA of an omega GST gene (<i>RpGSTO1</i>) from <i>R. padi</i>, which contains 720 bp in length and encodes 239 amino acids. A phylogenetic analysis revealed that RpGSTO1 belongs to the omega class of insect GSTs. RpGSTO1 gene was highly expressed in transformed <i>Escherichia coli</i> and the protein was purified by affinity chromatography. The recombinant RpGSTO1 displayed reduced glutathione (GSH)-dependent conjugating activity toward the substrate 1-chloro-2, 4-dinitrobenzene (CDNB) substrate. The recombinant RpGSTO1 protein exhibited optimal activity at pH 7.0 and 30°C. In addition, a disk diffusion assay showed that <i>E. coli</i> overexpressing RpGSTO1 increased resistance to cumene hydroperoxide-induced oxidative stress. Real-time quantitative PCR analysis showed that the relative expression level of <i>RpGSTO1</i> was different in response to different insecticides, suggesting that the enzyme could contribute to insecticide metabolism in <i>R. padi</i>. These findings indicate that RpGSTO1 may play a crucial role in counteracting oxidative stress and detoxifying the insecticides. The results of our study contribute to a better understanding the mechanisms of insecticide detoxification and resistance in <i>R. padi</i>.