Glutaredoxin 2 in the mud crab Scylla paramamosain : Identification and functional characterization under hypoxia and pathogen challenge

Glutaredoxin (Grx) is a glutathione-dependent oxidoreductase that plays a key role in antioxidant defense. In this study, a novel Grx2 gene ( SpGrx2 ) was identified from the mud crab Scylla paramamosain, which consists of a 196 bp 5′ untranslated region, a 357 bp open reading frame, and a 964 bp 3′ untranslated region. The putative SpGrx2 protein has a typical single Grx domain with the active center sequence C–P–Y–C. The expression analysis revealed that the SpGrx2 mRNA was most abundant in the gill, followed by the stomach and hemocytes. Both mud crab dicistrovirus-1 and Vibrio parahaemolyticus infection as well as hypoxia could differentially induce the expression of SpGrx2. Furthermore, silencing SpGrx2 in vivo affected the expression of a series of antioxidant-related genes after hypoxia treatment. Additionally, SpGrx2 overexpression significantly increased the total antioxidant capacity of Drosophila Schneider 2 cells after hypoxia, resulting in a reduction of reactive oxygen species and malondialdehyde content. The subcellular localization results indicated that SpGrx2 was localized in both the cytoplasm and the nucleus of Drosophila Schneider 2 cells. These results indicate that SpGrx2 plays a crucial role as an antioxidant enzyme in the defense system of mud crabs against hypoxia and pathogen challenge.