Cu,Zn superoxide dismutase from Trematomus bernacchii: functional conservation and erratic molecular evolution in Antarctic teleosts

Stress granules in Ciona robusta: First evidences of TIA-1-related nucleolysin and tristetraprolin gene expression under metal exposure

Stress granules are non-membranous cytoplasmic foci, composed of non-translating messenger ribonucleoproteins, translational initiation factors and other additional proteins. They represent a primary mechanism to rapidly modulate gene expression when cells are subjected to adverse environmental conditions. Very few works have been devoted to study the presence of the molecular components of stress granules in invertebrates. In this work, we characterized the transcript sequences for two important protein components of stress granules, TIA-1-related nucleolysin (TIAR) and tristetraprolin (TTP), in the solitary ascidian Ciona robusta, an invertebrate chordate, and carried out the first studies on their gene expression under stress conditions induced by metals (Cu, Zn and Cd). Data on mRNA expression levels, provided by qRT-PCR analyses, show a generalized decrease at the second day of metal-exposure for both tiar and ttp, suggesting that metal accumulation induces acute stress and the inhibition of the transcription for the two studied proteins. In-situ hybridization analyses demonstrate that TIAR and TTP antisense riboprobes recognize circulating granular amoebocytes in the hemolymph, in both blood lacunae and tunic. The results obtained in this work increase our knowledge on the evolution of anti-stress proteins in metazoans and emphasize the importance of the transcription of tiar and ttp, which represents an efficient physiological response allowing organisms to survive in the environment under stress conditions.

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

Three distinct superoxide dismutases (SODs)-copper/zinc-SOD (SOD1), manganese-SOD (SOD2), and extracellular copper/zinc-SOD (SOD3)-were identified from a primitive chondrostean fish, Acipenser baerii, enabling the comparison of their transcriptional regulation patterns during development, prelarval ontogeny, and immune stimulation. Each A. baerii SOD isoform (AbSOD) shared conserved structural features with its vertebrate orthologs; however, phylogenetic analyses hypothesized a different evolutionary history for AbSOD3 relative to AbSOD1 and AbSOD2 in the vertebrate lineage. The AbSOD isoforms showed different tissue distribution patterns; AbSOD1 was predominantly expressed in most tissues. The expression of the AbSOD isoforms showed isoform-dependent dynamic modulation according to embryonic development and prelarval ontogenic behaviors. Prelarval microinjections revealed that lipopolysaccharide only induced AbSOD3 expression, while Aeromonas hydrophila induced the expression of AbSOD2 and AbSOD3. In fingerlings, the transcriptional response of each AbSOD isoform to bacterial infection was highly tissue-specific, and the three isoforms exhibited different response patterns within a given tissue type; AbSOD3 was induced the most sensitively, and its induction was the most pronounced in the kidneys and skin. Collectively, these findings suggest isoform-dependent roles for the multigene SOD family in antioxidant defenses against the oxidative stress associated with development and immune responses in these endangered sturgeon fish.

Copper/Zinc Superoxide Dismutase from the Crocodile Icefish Chionodraco hamatus: Antioxidant Defense at Constant Sub-Zero Temperature

In the present study, we describe the purification and molecular characterization of Cu,Zn superoxide dismutase (SOD) from Chionodraco hamatus, an Antarctic teleost widely distributed in many areas of the Ross Sea that plays a pivotal role in the Antarctic food chain. The primary sequence was obtained using biochemical and molecular biology approaches and compared with Cu,Zn SODs from other organisms. Multiple sequence alignment using the amino acid sequence revealed that Cu,Zn SOD showed considerable sequence similarity with its orthologues from various vertebrate species, but also some specific substitutions directly linked to cold adaptation. Phylogenetic analyses presented the monophyletic status of Antartic Teleostei among the Perciformes, confirming the erratic differentiation of these proteins and concurring with the theory of the "unclock-like" behavior of Cu,Zn SOD evolution. Expression of C. hamatus Cu,Zn SOD at both the mRNA and protein levels were analyzed in various tissues, highlighting the regulation of gene expression related to environmental stress conditions and also animal physiology. The data presented are the first on the antioxidant enzymes of a fish belonging to the Channichthyidae family and represent an important starting point in understanding the antioxidant systems of these organisms that are subject to constant risk of oxidative stress.

Characterizations of intracellular copper/zinc superoxide dismutase from yellow drum (Nibea albiflora, Richardson 1846) and its gene expressions under the ammonia/nitrite stress

Intracellular copper/zinc superoxide dismutase (icCuZnSOD) is a member of superoxide dismutase family that is capable of catalyzing the superoxide radicals into either hydrogen peroxide (H₂O₂) or ordinary molecular oxygen (O₂). Unlike mammals, the study of icCuZnSOD in aquatic animals is still in the infancy stage. Here, we identified the cDNA of na-iccuznsod from yellow drum (Nibea albiflora, Richardson 1846) and obtained its fusion protein for the first time. The mRNA expressions of na-iccuznsod were investigated in different tissues, and the dominant distribution was found in head-kidney, followed by brain, liver, heart, and gill. The effects of ammonia-N/nitrite-N on the mRNA expressions of na-iccuznsod were investigated. Na-iccuznsod transcription levels showed a general tendency of an initial up-regulation followed by a down-regulation in liver, gill, and head-kidney when yellow drum were exposed to ammonia-N/nitrite-N at the lethal concentration 50 at 96 h post-treatment, suggesting the important role of Na-icCuZnSOD in eliminating reactive oxygen species (ROS) induced by ammonia-N/nitrite-N. In addition, the characteristics of Na-icCuZnSOD protein and its comparative analysis with Na-ecCuZnSOD were investigated. Na-icCuZnSOD protein showed high enzyme stabilities over a wide range of temperature (10 to 60 °C) and pH (4.9 to 11.0), indicating its broad in vitro applications in many industries. Furthermore, the comparative analysis of Na-icCuZnSOD and Na-ecCuZnSOD gives a new perspective for the study of their structure-function relationship. Collectively, the present study will advance our understanding of the toxicity of ammonia-N/nitrite-N on yellow drum through testing the mRNA expression of iccuznsod gene, and broaden our knowledge of the protein characteristics of icCuZnSOD from fish.

Cu,Zn Superoxide Dismutase Genes in Tribolium castaneum: Evolution, Molecular Characterisation, and Gene Expression during Immune Priming

The production of reactive oxygen species (ROS) is a normal consequence of the aerobic cell metabolism. Despite their high and potentially detrimental reactivity with various biomolecules, the endogenous production of ROS is a vital part of physiological, immunological, and molecular processes that contribute to fitness. The role of ROS in host-parasite interactions is frequently defined by their contribution to innate immunity as effectors, promoting parasite death during infections. In vertebrates, ROS and antioxidant system enzymes, such as superoxide dismutase (SOD) are also involved in acquired immune memory, where they are responsible for T-cell signalling, activation, proliferation, and viability. Based on recent findings, ROS are now also assumed to play a role in immune priming, i.e., a form of memory in invertebrates. In this study, the potential involvement of Cu,Zn SODs in immunity of the red flour beetle Tribolium castaneum is described for the first time, applying an approach that combines an in silico gene characterisation with an in vivo immune priming experiment using the Gram-positive entomopathogen Bacillus thuringiensis. We identified an unusually high number of three different transcripts for extracellular SOD and found that priming leads to a fine-tuned modulation of SOD expression, highlighting the potential of physiological co-adaptations for immune phenotypes.

Peroxiredoxin 6 from the Antarctic emerald rockcod: molecular characterization of its response to warming

In the present study, we describe the purification and molecular characterization of two peroxiredoxins (Prdxs), referred to as Prdx6A and Prdx6B, from Trematomus bernacchii, a teleost widely distributed in many areas of Antarctica, that plays a pivotal role in the Antarctic food chain. The two putative amino acid sequences were compared with Prdx6 orthologs from other fish, highlighting a high percentage of identity and similarity with the respective variant, in particular for the residues that are essential for the characteristic peroxidase and phospholipase activities of these enzymes. Phylogenetic analyses suggest the appearance of the two prdx6 genes through a duplication event before the speciation that led to the differentiation of fish families and that the evolution of the two gene variants seems to proceed together with the evolution of fish orders and families. The temporal expression of Prdx6 mRNA in response to short-term thermal stress showed a general upregulation of prdx6b and inhibition of prdx6a, suggesting that the latter is the variant most affected by temperature increase. The variations of mRNA accumulation are more conspicuous in heart than the liver, probably related to behavioral changes of the specimens in response to elevated temperature. These data, together with the peculiar differences between the molecular structures of the two Prdx6s in T. bernacchii as well as in the tropical species Stegastes partitus, suggest an adaptation that allowed these poikilothermic aquatic vertebrates to colonize very different environments, characterized by different temperature ranges.

Intracellular Copper Zinc Superoxide dismutase (icCuZnSOD) from Asian seabass (Lates calcarifer): molecular cloning, characterization and gene expression with reference to Vibrio anguillarum infection

Copper Zinc Superoxide dismutase (CuZnSOD) is the family of most important antioxidant metalloenzymes that protects tissues from damage by reactive oxygen species (ROS). In the present study, the intracellular copper zinc SOD from the Asian seabass Lates calcarifer (Lc-icCuZnSOD) was identified by RNA ligase mediated rapid amplification of cDNA ends (RLM-RACE) technique. The full-length cDNA of Lc-icCuZnSOD consisted of 809 nucleotides with an open-reading frame of 465 bp encoding 154 amino acids and N-Glycosylation site (NVTA) within. The predicted molecular mass of the protein is 15.84 kDa with an estimated pI of 5.52. The deduced amino acid sequence of Lc-icCuZnSOD shared high degree of homology with known CuZnSODs from other species. CuZn binding sites (H47, H49, H64, and H121 for Cu(2+) and H72, H81, and ASP84 for Zn(2+)), two cysteine residues (aa 58 and 147) that form a disulfide bond, and CuZnSOD family signature sequences (GFHVHAFGDNT, aa 45-55 and GNAGGRLACGVI, aa 139-150) were highly conserved among fish species. Temporal and tissue specific expression of Lc-icCuZnSOD was significantly differentially altered in Asian seabass challenged with Vibrio anguillarum indicating possible role in antioxidant activities involved in the innate immune defense mechanisms.