Molecular cloning, mRNA expression and functional characterization of a catalase from Chinese black sleeper (Bostrychus sinensis)

Molecular characterization of a catalase gene in the freshwater green alga Closterium ehrenbergii and its putative function against abiotic stresses

Catalases (CATs) are ubiquitous antioxidant enzymes that prevent cellular oxidative damage through the decomposition of H2O2. However, there is relatively little information on CAT in the worldwide-distributed freshwater green alga Closterium ehrenbergii. Here, we cloned the full-length catalase cDNA from C. ehrenbergii (CeCAT) and characterized its structural features and expressional responses against aquatic contaminants. The open reading frame of CeCAT was determined to be 1476 bp, encoding 491 amino acids with a theoretical molecular mass of 56.1 kDa. The CeCAT protein belongs to the NADPH-binding CAT family and might be located in the cytosol. BLAST and phylogenetic results showed that CeCAT had a high identity with CAT proteins from other microalgae and the water lily Nymphaea colorata (Streptophyta). The transcriptional levels of CeCAT were significantly upregulated by the metal copper and herbicide atrazine, but little affected by other tested metals (Ni and Cr) and endocrine-disrupting chemicals (polychlorinated biphenyl, PCB). The maximum expression was registered under 0.1 mg/L CuCl2 and 0.2 mg/L CuSO4 exposures. In addition, excess copper considerably increased production of reactive oxygen species in the cells. These results suggest that CeCAT may function to defend against oxidative stress in green algae and can respond specifically to different kinds of metals and herbicides.

The combination of high temperature and Vibrio infection worsens summer mortality in the clam Meretrix petechialis by increasing apoptosis and oxidative stress

The interaction between environmental factors and Vibrio in bivalves is not well understood, despite the widely held belief that pathogen infection and seawater temperature significantly impact summer mortality. In the present study, we conducted simulated experiments to explore the effects of high temperature and Vibrio infection on the clam Meretrix petechialis. The survival curve analysis revealed that the combined challenge of high temperature and Vibrio infection (31°C-vibrio) led to significantly higher clam mortality compared to the groups exposed solely to Vibrio (27°C-vibrio), high temperature (31°C-control), and the control condition (27°C-control). Furthermore, PCoA analysis of 11 immune genes indicated that Vibrio infection predominated during the incubation period, with a gradual equilibrium between these factors emerging during the course of the infection. Additionally, our investigations into apoptosis and autophagy processes exhibited significant induction of mTOR and Bcl2 of the 31°C-vibrio group in the early challenge stage, followed by inhibition in the later stage. Oxidative stress analysis demonstrated a substantial additive effect on malondialdehyde (MDA) and glutathione (GSH) content in the combined challenge group compared to the control group. Comparative transcriptome analysis revealed a significant increase in differentially expressed genes related to immunity, such as complement C1q-like protein, C-type lectin, big defensin, and lysozyme, in the 31°C-vibrio group, suggesting that the synergistic effect of high temperature and Vibrio infection triggers more robust antibacterial immune responses. These findings provide critical insights for understanding the infection process and uncovering the causes of summer mortality.

Antioxidant Defence in Labeo rohita to Biotic and Abiotic Stress: Insight from mRNA Expression, Molecular Characterization and Recombinant Protein-Based ELISA of Catalase, Glutathione Peroxidase, CuZn Superoxide Dismutase, and Glutathione S-Transferase

Fish possess numerous enzymatic antioxidant systems as part of their innate immunity. These systems have been poorly studied in Labeo rohita (rohu). The present study characterized and investigated the role of antioxidant genes in the defence mechanisms against two types of stressors, including infection and ammonia stress. Four key genes associated with antioxidant activity-catalase, glutathione peroxidase, glutathione S-transferase, and CuZn superoxide dismutase were successfully cloned and sequenced. These genes were found to be expressed in different tissues and developmental stages of rohu. The expression levels of these antioxidant genes in the liver and anterior kidney tissues of rohu juveniles were modulated in response to bacterial infection (Aeromonas hydrophila), parasite infection (Argulus siamensis), poly I:C stimulation and ammonia stress. Additionally, the recombinant proteins derived from these genes exhibited significant antioxidant and antibacterial activities. These proteins also demonstrated a protective effect against A. hydrophila infection in rohu and had an immunomodulatory role. Furthermore, indirect ELISA assay systems were developed to measure these protein levels in healthy as well as A. hydrophila and ammonia-induced rohu serum. Overall, this study characterized and emphasised the importance of the antioxidant mechanism in rohu's defence against oxidative damage and microbial diseases.

Molecular Cloning and Functional Characterization of Catalase in Stress Physiology, Innate Immunity, Testicular Development, Metamorphosis, and Cryopreserved Sperm of Pacific Abalone

Catalase is a crucial enzyme of the antioxidant defense system responsible for the maintenance of cellular redox homeostasis. The aim of the present study was to evaluate the molecular regulation of catalase (Hdh-CAT) in stress physiology, innate immunity, testicular development, metamorphosis, and cryopreserved sperm of Pacific abalone. Hdh-CAT gene was cloned from the digestive gland (DG) of Pacific abalone. The 2894 bp sequence of Hdh-CAT had an open reading frame of 1506 bp encoding 501 deduced amino acids. Fluorescence in situ hybridization confirmed Hdh-CAT localization in the digestive tubules of the DG. Hdh-CAT was induced by different types of stress including thermal stress, H₂O₂ induction, and starvation. Immune challenges with Vibrio, lipopolysaccharides, and polyinosinic-polycytidylic acid sodium salt also upregulated Hdh-CAT mRNA expression and catalase activity. Hdh-CAT responded to cadmium induced-toxicity by increasing mRNA expression and catalase activity. Elevated seasonal temperature also altered Hdh-CAT mRNA expression. Hdh-CAT mRNA expression was relatively higher at the trochophore larvae stage of metamorphosis. Cryopreserved sperm showed significantly lower Hdh-CAT mRNA expression levels compared with fresh sperm. Hdh-CAT mRNA expression showed a relationship with the production of ROS. These results suggest that Hdh-CAT might play a role in stress physiology, innate immunity, testicular development, metamorphosis, and sperm cryo-tolerance of Pacific abalone.

Cu/Zn Superoxide Dismutase and Catalase of Yangtze Sturgeon, Acipenser dabryanus: Molecular Cloning, Tissue Distribution and Response to Fasting and Refeeding

Superoxide dismutase and catalase are two major antioxidant enzymes in the fish antioxidant defense system, which can remove excess reactive oxygen species and protect fish from stress-induced oxidative damage. The present study aimed to clone the sequences of Yangtze sturgeon, Acipenser dabryanus, Cu/Zn superoxide dismutase (AdCu/Zn-SOD) and catalase (AdCAT), and to explore changes of gene expression in the liver and intestine during fasting and refeeding. A total of 120 fish were exposed to four fasting and refeeding protocols (fasting for 0, 3, 7, or 14 d and then refeeding for 14 d). The coding sequences of AdCu/Zn-SOD and AdCAT encoded 155 and 526 amino acid proteins, respectively, both of which were expressed mainly in the liver. During fasting, when compared to the control group, liver AdCu/Zn-SOD expression was significantly higher in the 3- and 14-d groups, whereas its intestinal expression increased significantly only in the 7-d group. Liver AdCAT expression increased significantly in the 3-, 7-, and 14-d groups. During refeeding, liver AdCu/Zn-SOD expression increased significantly in the 3-, 7-, and 14-d groups compared with those in the control group. Similarly, intestinal AdCu/Zn-SOD expression increased significantly in the 3- and 7-d groups. Moreover, intestinal AdCAT expression was significantly higher in the 3-d group than in the control group, but decreased significantly in the 14-d group. Our findings indicated that AdCu/Zn-SOD and AdCAT play important roles in protecting fish against starvation-induced oxidative stress. Yangtze sturgeon exhibited the potential to adapt to a starvation and refeeding regime.

Identification and characterization of the c-type lysozyme gene from a marine fish, Bostrychus sinensis

In this study, a c-type lysozyme gene (BsLyzC) was identified and characterized from a marine fish, Bostrychus sinensis. The BsLyzC encodes 154 amino acids and contains a signal peptide of 17 amino acids, two catalytic residues and eight cysteine residues. The genomic DNA of BsLyzC consists of four exons and three introns. The BsLyzC shares high sequence similarity with c-type lysozyme from other fish species. The qPCR assays indicated that the BsLyzC exhibited a constitutive expression pattern in eleven examined tissues of healthy B. sinensis individuals. The transcripts of BsLyzC could be significantly induced after infection of Vibrio parahemolyticus in blood, spleen and head kidney. The optimal temperature and pH for recombinant BsLyzC (rBsLyzC) were found to be 50 °C and 6.0, respectively. The rBsLyzC exhibited antibacterial activities against two Gram-positive bacteria and two Gram-negative bacteria. These results indicate that the BsLyzC is involved in the antibacterial immunity of B. sinensis.

Updating the use of biochemical biomarkers in fish for the evaluation of alterations produced by pharmaceutical products

The evaluation of toxic effects in stressful environmental conditions can be determined through the imbalance between exogenous factors (environmental contaminants) and enzymatic and non-enzymatic defenses in biological systems. The use of fish for the identification of alterations in biochemical biomarkers provides a comprehensive vision of the effects that pharmaceutical products cause in the aquatic ecosystem, as they are organisms with high sensitivity to contaminants, filtering capacity, and potential for environmental toxicology studies. A wide range of pharmaceuticals can stimulate or alter a variety of biochemical mechanisms, such as oxidative damage to membrane lipids, proteins, and changes in antioxidant enzymes. This review includes a summary of knowledge of the last 20 years, in the understanding of the different biochemical biomarkers generated by exposure to pharmaceuticals in fish, which include different categories of pharmaceutical products: NSAIDs, analgesics, antibiotics, anticonvulsants, antidepressants, hormones, lipid regulators and mixtures. This review serves as a tool in the design of studies for the evaluation of the effects of pharmaceutical products, taking into account the most useful biomarkers, type of matrix, enzyme alterations, all taking the pharmaceutical group of interest.