Molecular characterization of a novel thioredoxin-related transmembrane protein gene AcTMX3 that plays important roles in antioxidant defence in Arma chinensis diapause.

Protein disulphide isomerase (PDI) possesses disulphide isomerase, oxidoreductase and molecular chaperone activities, and is involved in regulating various physiological processes. However, there are few studies on the function in insect diapause. In this study, we cloned one novel member PDI family (TMX3, thioredoxin-related transmembrane protein 3) in Arma chinensis. The AcTMX3 encodes 426 amino acids that contains a predicted N-terminal signal sequence, a thioredoxin-like domain with the CXXC active site and a potential transmembrane region, which are typical sequence features of TMX3. RT-qPCR results showed that AcTMX3 was mainly expressed in the head under non-diapause conditions, while AcTMX3 was highly expressed in the fat body (central metabolic organ) under diapause conditions. Moreover, temporal expression profile showed that compared with non-diapause conditions, diapause conditions significantly induced AcTMX3 expression, and the expression of AcTMX3 was enhanced at 15°C. Silencing AcTMX3 in A. chinensis significantly inhibited the expression of antioxidant genes (AcTrx2 and AcTrx-like), increased the content of H₂O₂ and ascorbate and reduced the survival rate of A. chinensis under diapause conditions. Our results suggested that AcTMX3 played an important role in the resistance of A. chinensis to oxidative stress under diapause conditions.