Characterization of Copper/Zinc-Superoxide Dismutase (Cu/Zn-SOD) Gene from an Endangered Freshwater Fish Species Hemibarbus mylodon (Teleostei; Cypriniformes)

Abstract

Gene structure of copper/zinc-superoxide dismutase (Cu/Zn-SOD; sod1) was characterized in Hemibarbus mylodon (Teleostei; Cypriniformes), an endangered freshwater fish species in Korean peninsula. Full-length cDNA of H. mylodon SOD1 consisted of a 796-bp open reading frame sequence encoding 154 amino acids, and the deduced polypeptide sequence shared high sequence homology with other orthologs, particularly with regard to metal-coordinating ligands. Genomic structure of the H. mylodon sod1 gene (hmsod1; 1,911 bp from the ATG start codon to the stop codon) was typical quinquepartite (i.e., five exons interrupted by four introns); the lengths of the exons were similar among species belonging to various taxonomic positions. The molecular phylogeny inferred from sod1 genes in the teleost lineage was in accordance with the conventional taxonomic assumptions. 5'-flanking upstream region of hmsod1, obtained using the genome walking method, contained typical TATA and CAAT boxes. It also showed various transcription factor binding motifs that may be potentially involved in stress/immune response (e.g., sites for activating proteins or nuclear factor kappa B) or metabolism of xenobiotic compounds (e.g., xenobiotic response element; XRE). The hmsod1 transcripts were ubiquitously detected among tissues, with the liver and spleen showing the highest and lowest expression, respectively. An experimental challenge with Edwardsiella tarda revealed significant upregulation of the hmsod1 in kidney (4.3-fold) and spleen (3.1-fold), based on a real-time RT-PCR assay. Information on the molecular characteristics of this key antioxidant enzyme gene could be a useful basis for a biomarker-based assay to understand cellular stresses in this endangered fish species.

Superoxide Dismutase Multigene Family from a Primitive Chondrostean Sturgeon, Acipenser baerii: Molecular Characterization, Evolution, and Antioxidant Defense during Development and Pathogen Infection

“…The lack of splenic upregulation in this study is broadly similar to findings from A. hydrophila -challenged yellow catfish, Pelteobagrus fulvidraco [ 112 ], and with the suppressed expression of immune/stress-responsive genes in the carp Cyprinus carpio during A. hydrophila challenge [ 113 ]. However, our findings are in contrast to other previous results from tilapia, Oreochromis niloticus [ 114 ]; yellow drum, N. albiflora [ 115 ]; and Korean spotted barbel, H. mylodon [ 116 ], which all suggest that the splenic upregulation of SOD is involved in antioxidant defense during bacterial infection. Because we were able to observe the significant induction of several marker genes involved in inflammation, antimicrobial defense, and/or iron sequestration (such as interleukin-1β, hepcidin, and transferrin) in the spleens of challenged individuals (data not shown), it may be assumed that the combating of infection-driven oxidative stress might not rely so much on the induction of AbSOD transcription in the spleens of A. baerii fingerlings.…”