A novel theta-class glutathione S-transferase gene in Rhopalosiphum padi (L.) (Hemiptera: Aphididae): Identification, recombinant protein expression and function analyses of RpGSTT1

Abstract

Glutathione S-transferases (GSTs) play a major role in the detoxification of insecticides and the protection against oxidative damage caused by ROS (reactive oxygen species). The bird cherry-oat aphid, Rhopalosiphum padi (L.), is a major crop pest worldwide. Chemical insecticides are currently used to control aphids, but insecticide resistance is an evolutionary issue for aphid control. In this research, we identified and cloned the full-length cDNA of a theta-class GST gene (RpGSTT1) from R. padi, which contains 702 bp open reading frame encoding 233 amino acids. RpGSTT1 was clustered together with theta classe of insect GSTs in the phylogenetic tree. Effect of insecticide exposure on the GST enzyme activity was investigated in vivo. After affinity purification, the recombinant RpGSTT1 protein was able to catalyze the conjugation of 1-chloro-2, 4-dinitrobenzene (CDNB). A disc diffusion assay showed that the RpGSTT1 can increase resistance to cumene hydroperoxide-induced oxidative stress. In addition, the purified recombinant RpGSTT1 protected super-coiled DNA from oxidative damage. By quantitative PCR, The relative expression level of RpGSTT1 in the aphid was highly up-regulated after 12 h exposure to β-cypermethrin, isoprocarb, malathion and sulfoxaflor, respectively. To our knowledge, RpGSTT1 is the first theta class of GST gene reported in bird cherry-oat aphid. Our findings indicate that RpGSTT1 may be involved in insecticide detoxification in R. padi.