Identification and analysis of a Cu/Zn superoxide dismutase from Haliotis diversicolor supertexta with abalone juvenile detached syndrome

Molecular characterization, purification, and antioxidant activity of recombinant superoxide dismutase from the Pacific abalone Haliotis discus hannai Ino

Superoxide dismutase (SOD) is an acidic metalloenzyme that scavenges free radicals produced by endogenous and exogenous substances. In the present study, the tissue distribution of the superoxide dismutase HdhCu/Zn-SOD was investigated in Haliotis discus hannai Ino. The expression profile after lipopolysaccharide (LPS) challenge was determined using quantitative real-time polymerase chain reaction (qPCR). To study the antioxidant activity of a recombinant HdhCu/Zn-SOD protein, the HdhCu/Zn-SOD gene was cloned into the pPIC9K vector and transformed into the Pichia pastoris GS115 strain by electroporation. After induction by methanol, the recombinant product was purified using immobilized metal affinity chromatography and confirmed using mass spectrometry. The optimal expression conditions were determined to be incubation with 0.5% methanol at pH 6.0, resulting in a stable expressed product with the molecular weight of approximately 17 kDa and 21 kDa. The enzymatic activity of HdhCu/Zn-SOD consistently increased with increasing Cu²⁺ concentrations and showed good thermal stability. Recombinant HdhCu/Zn-SOD showed a strong ability to scavenge superoxide anions and hydroxyl radicals and protected L929 cells against the toxicity caused by H₂O₂ through its in vitro antioxidant activity. The heterologous expression of HdhCu/Zn-SOD in P. pastoris and the antioxidant activity of this enzyme are reported for the first time.

Transcriptome Analysis Revealed Changes of Multiple Genes Involved in Haliotis discus hannai Innate Immunity during Vibrio parahemolyticus Infection

Abalone (Haliotis discus hannai) is one of the most valuable marine aquatic species in Korea, Japan and China. Tremendous exposure to bacterial infection is common in aquaculture environment, especially by Vibrio sp. infections. It’s therefore necessary and urgent to understand the mechanism of H. discus hannai host defense against Vibrio parahemolyticus infection. However studies on its immune system are hindered by the lack of genomic resources. In the present study, we sequenced the transcriptome of control and bacterial challenged H. discus hannai tissues. Totally, 138 MB of reference transcriptome were obtained from de novo assembly of 34 GB clean bases from ten different libraries and annotated with the biological terms (GO and KEGG). A total of 10,575 transcripts exhibiting the differentially expression at least one pair of comparison and the functional annotations highlight genes related to immune response, cell adhesion, immune regulators, redox molecules and mitochondrial coding genes. Mostly, these groups of genes were dominated in hemocytes compared to other tissues. This work is a prerequisite for the identification of those physiological traits controlling H. discus hannai ability to survive against Vibrio infection.

The early stages of the immune response of the European abalone Haliotis tuberculata to a Vibrio harveyi infection

Vibrio harveyi is a marine bacterial pathogen responsible for episodic abalone mortalities in France, Japan and Australia. In the European abalone, V. harveyi invades the circulatory system in a few hours after exposure and is lethal after 2 days of infection. In this study, we investigated the responses of European abalone immune cells over the first 24 h of infection. Results revealed an initial induction of immune gene expression including Rel/NF-kB, Mpeg and Clathrin. It is rapidly followed by a significant immuno-suppression characterized by reduced cellular hemocyte parameters, immune response gene expressions and enzymatic activities. Interestingly, Ferritin was overexpressed after 24 h of infection suggesting that abalone attempt to counter V. harveyi infection using soluble effectors. Immune function alteration was positively correlated with V. harveyi concentration. This study provides the evidence that V. harveyi has a hemolytic activity and an immuno-suppressive effect in the European abalone.

Identification and analysis of an intracellular Cu/Zn superoxide dismutase from Sepiella maindroni under stress of Vibrio harveyi and Cd2+

Superoxide dismutases (SODs) are ubiquitous family of metalloenzymes involved in protecting organisms from excess reactive oxygen species damage. In this paper, a novel intracellular Cu/ZnSOD from Sepiella maindroni (designated as SmSOD) was identified and characterized. The full-length cDNA sequence of SmSOD (GenBank accession No. KF908850) was 709 bp containing an open reading frame (ORF) of 459 bp, encoding 153 amino acid residues peptide with predicted pI/MW (6.02/15.75 kDa), a 131 bp-5'- and 116 bp-3'- untranslated region (UTR). BLASTn analysis and phylogenetic relationship strongly suggested that the sequence shared high similarity with known Cu/Zn SODs. Several highly conserved motifs, including two typical Cu/Zn SOD family domains, two conserved Cu-/Zn-binding sites (H-47, H-49, H-64, H-120 for Cu binding, and H-64, H-72, H-81, D-84 for Zn binding) and intracellular disulfide bond (C-58 and C-146), were also identified in SmSOD. Time-dependent mRNA expression of SmSOD in hepatopancreas was recorded by quantitative real-time RT-PCR after Vibrio harveyi injection and Cd(2+) exposure. The results indicated that SmSOD was an acute-phase protein involved in the immune responses against pathogens and biological indicator for metal contaminants in aquatic environment.

Molecular characterization of a manganese superoxide dismutase and copper/zinc superoxide dismutase from the mussel Mytilus galloprovincialis

The full-length cDNA sequences coding respectively for a manganese superoxide dismutase (Mg-MnSOD) and copper/zinc superoxide dismutase (Mg-CuZnSOD) were cloned from Mytilus galloprovincialis. Mg-MnSOD and Mg-CuZnSOD cDNAs encoded a polypeptide of 228 and 211 amino acids, respectively. Sequence analysis indicated Mg-MnSOD was a mitochondrial MnSOD and Mg-CuZnSOD was an intracellular CuZnSOD. Multiple alignment analysis showed that both Mg-MnSOD and Mg-CuZnSOD sequences had the common features conserved in MnSODs and CuZnSODs, respectively. Phylogenetic analysis revealed that Mg-MnSOD clustered together with MnSODs from other mollusks, whereas Mg-CuZnSOD clustered with other mollusk intracellular CuZnSODs with a wider phylogenetic distance. By quantitative real-time RT-PCR (qPCR) analysis, both Mg-MnSOD and Mg-CuZnSOD transcripts were detected in all tissues examined with the highest expression level in hepatopancreas. Following bacterial challenge, the expression level of Mg-MnSOD and Mg-CuZnSOD increased first and subsequently decreased to the original level in hemocytes. In hepatopancreas, Mg-CuZnSOD mRNA was up-regulated significantly at 72 h and 96 h post challenge, while the level of Mg-MnSOD transcript had no significant change. Therefore, Mg-MnSOD and Mg-CuZnSOD expressions were inducible and they were probably involved in the immune response against bacterial challenge. These results suggest that these SODs may play important roles in the immune defense system of M. galloprovincialis and perhaps contribute to the protective effects against oxidative stress in this mussel.

High-level expression of a sika deer (Cervus nippon) Cu/Zn superoxide dismutase in Pichia pastoris and its characterization

Production of a sika deer Cu/Zn-SOD was achieved in Pichia pastoris after the reconstituted expression vector pPIC9K was transformed into the strain GS115. By employing Saccharomyces cerevisiae secretion signal peptide (α-factor) under the regulation of the methanol-inducible promoter of the gene of alcohol oxidase 1 (AOX1), sika deer Cu/Zn-SOD with a molecular mass of 16kDa was expressed while recombinant sika deer Cu/Zn-SOD with an activity of 3500U/mL was obtained from a 5L bioreactor. After two successive steps of chromatography on DEAE-650C and Superdex75, recombinant sika deer Cu/Zn-SOD was obtained with 13.8% yield, 14.5-fold purification, and a specific activity of 3447U/mg. Its optimum temperature and optimum pH were 40°C and 7.0, respectively.

Research progress on the mollusc immunity in China

The economical and phylogenic importance of mollusc has led an increasing number of investigations giving emphasis to immune defense mechanism. This review discusses the advances in immunological study of mollusc in China, with special reference to dominant aquaculture species over the past decades. As an invertebrate group, molluscs lack adaptive immunity and consequently they have evolved sophisticated strategies of innate immunity for defense against pathogens. This review aims to present the various immunologically significant pattern recognition receptors (PRRs), such as Toll-like receptors (TLRs), lectins, lipopolysaccharide and β-1, 3-glucan binding protein (LGBP), scavenger receptors (SRs) employed by mollucans. This work also highlights immune proteolytic cascade, TLR signaling pathway and an extensive repertoire of immune effectors including antimicrobial peptide, lysozyme, antioxidant enzyme and heat shock protein. Further, the review presents the preliminary progress made on the catecholaminergic neuroendocrine system in scallop and its immunomodulation function to throw light into neuroendocrine-immune regulatory network in lower invertebrates.

Transcriptional regulation of selenium-dependent glutathione peroxidase from Venerupis philippinarum in response to pathogen and contaminants challenge

Glutathione peroxidases (GPx) are key enzymes in the antioxidant systems of living organisms by catalyzing the reduction of peroxides to non-reactive products. In the present study, the full-length cDNA encoding a selenium-dependent GPx was identified from Venerupis philippinarum (designated as VpSe-GPx), and the spatial and temporal expression patterns post-Vibrio anguillarum, heavy metals and benzo[a]pyrene (B[a]P) challenge were also investigated. VpSe-GPx possessed all the conserved features critical for the fundamental structure and function of glutathione peroxidase. The VpSe-GPx mRNA was found to be most abundantly expressed in hepatopancreas. Vibrio challenge could significantly up-regulate the mRNA expression of VpSe-GPx, and the highest expression level was detected at 24 h post-infection with 6.5-fold increase compared with that in the control group. For heavy metals exposure, the expression of VpSe-GPx was significantly induced by 20, 40 μg L(-1) Cd and 10, 20 μg L(-1) Cu but depressed by 10 μg L(-1) Cd and 40 μg L(-1) Cu. With regards to B[a]P exposure, the expression of VpSe-GPx mRNA was significantly induced at 48 and 96 h post challenge. All these results suggested that VpSe-GPx was potentially involved in mediating the immune response and antioxidant defense in V. Philippinarum.