Molecular identification and characterization of the superoxide dismutase (SOD) gene family in Tetranychus urticae (Acari: Tetranychidae) and the role of TuSOD2 gene under short-term heat stress.

Superoxide dismutases (SODs) are key enzymes for scavenging insects' excess reactive oxygen species (ROS) and play a crucial role in resisting a variety of stresses. The deletion of SOD genes can alter the response of insects to abiotic stresses. In this study, four genes of the superoxide dismutase family in Tetranychus urticae were identified and analyzed, among which three copper/zinc SODs and a manganese SOD. The result of quantitative real-time PCR showed that TuSOD2 expression level was up-regulated significantly under short-term heat stress, but TuSOD1, TuSOD2, and TuSOD4 were down-regulated or no significant difference, which indicated that T. urticae responded to oxidative stress induced by heat stress by raising the expression level of superoxide dismutase gene. Among them, TuSOD2 gene plays a key role in response to heat stress in T. urticae, and other SOD genes may be responsible for other oxidative stresses. RNA interference experiments showed that the knocking down of TuSOD2 reduced the activities of various antioxidant enzymes, resulting in a decline in the tolerance to high temperature and an increase in the mortality of T. urticae under short-term heat stress. To summarize, SOD, especially TuSOD2 plays an important role in treating short-term heat stress in T. urticae.