Molecular identification of two thioredoxin genes and their function in antioxidant defense in diapause.

Thioredoxin (Trx), an important part of thioredoxin systems, plays crucial role in maintaining the intracellular redox balance by scavenging reactive oxygen species (ROS). However, few Trxs have been functionally characterized in , especially in diapause. In this study, diapause induction condition promoted hydrogen peroxide accumulation and increased CAT enzymatic activity and ascorbate content, suggesting that was exposed to high level of ROS. Therefore, we identified and , and investigated the relationship with antioxidant defense. It was found that expression was significantly induced, whereas expression was the highest on day 10 under diapause conditions. The expression of and in fat body, a central metabolic organ of resisting oxidative stress, was significantly increased under diapause conditions, and was significantly improved by 5/15°C (diapause temperature). We investigated the knockdown of and in and found that some selected antioxidant genes were upregulated, indicating that the upregulated genes may be functional compensation for and silencing. We also found that the enzymatic activities of SOD and CAT, and the metabolite contents of hydrogen peroxide, ascorbate increased after and knockdown. These results suggested the and may play critical roles in antioxidant defense of diapause.