Glutaredoxins and thioredoxin peroxidase involved in defense of emamectin benzoate induced oxidative stress in Grapholita molesta.

Abstract

Glutaredoxins (Grxs) and thioredoxin peroxidases (Tpxs) are major antioxidant enzyme families involved in regulating cellular redox homeostasis and in defense of enhanced oxidative stress through scavenging reactive oxygen species (ROS). However, the functions of these enzymes have not been reported in the oriental fruit moth, Grapholita molesta (Busck), a worldwide pest of stone and pome fruits. Here, we identified four new antioxidant genes, GmGrx, GmGrx3, GmGrx5, and GmTpx which were induced by exposure with emamectin benzoate, a commonly used biopesticide for G. molesta control. Other environmental factors (low and high temperatures, Escherichia coli and Metarhizium anisopliae) also significantly induced the expression of these genes. After GmGrx or GmTpx silenced by RNA interference (RNAi), the percentage of larval survival to emamectin benzoate were significantly decreased, demonstrating that GmGrx and GmTpx are involved in protecting G. molesta from stresses induced by emamectin benzoate. Furthermore, silenced GmGrx, GmGrx3, GmGrx5, or GmTpx significantly enhanced the enzymatic activities of superoxide dismutase (SOD) (except GmTpx) and peroxidase (POD), as well as the contents of hydrogen peroxide and metabolites ascorbate. Taken together, our results suggest that GmGrx, GmGrx3, GmGrx5, and GmTpx may play critical roles in antioxidant defense. Specially, GmGrx and GmTpx contribute to the defense of oxidative damage induced by exposure to emamectin benzoate through scavenging excessive ROS in G. molesta. Our findings provided a theoretical basis for understanding functions of insect glutaredoxin and peroxidase systems.