Two superoxide dismutases (SODs) respond to bacterial challenge identified in the marbled eel Anguilla marmorata

Abstract

As the prime antioxidant enzymes, superoxide dismutases (SODs) can prevent oxidative stress caused by excessive reactive oxygen species (ROS) in living organisms. In this study, we identified two distinct members of SOD family from the marbled eel Anguilla marmorata (denoted as AmMnSOD and AmCu/ZnSOD) using homology cloning and rapid amplification of cDNA ends (RACE). The structural analysis revealed common features of SOD family in both AmSODs from primary to tertiary levels, including two MnSOD signature motifs and two Cu/ZnSOD signature motifs in AmMnSOD and AmCu/ZnSOD, respectively. Phylogenic analysis indicated that AmMnSOD and AmCu/ZnSOD proteins were both within fish monophyletic clade. The tissue distribution analysis demonstrated that AmMnSOD and AmCu/ZnSOD were expressed at higher levels in muscles and livers. The time-course dynamic expressions of AmSODs were observed through the experimental challenges with Aeromonas hydrophila, which were all significantly altered in gills, kidneys and livers. Results of the enzyme activity and western blot analysis also showed that the dynamic changes of AmSODs at the enzyme activity and protein levels were all regulated by A. hydrophila challenge. The overall results suggested that the AmSODs played crucial roles in innate immunity of A. marmorata, and our findings provided useful evidence for further understanding the modulation mechanism of SODs in the innate immune system of eels.