Molecular, transcriptional and functional delineation of Galectin-8 from black rockfish (Sebastes schlegelii) and its potential immunological role

Galectin-8-like isoform X1 mediates antibacterial, antiviral, and antioxidant responses in red-lip mullet (Planiliza haematocheilus) through positive modulation of pro-inflammatory cytokine, chemokine, and enzymatic antioxidant activity

Galectin 8 belongs to the tandem repeat subclass of the galectin superfamily. It possesses two homologous carbohydrate recognition domains linked by a short peptide and preferentially binds to β-galactoside-containing glycol-conjugates in a calcium-independent manner. This study identified Galectin-8-like isoform X1 (PhGal8X1) from red-lip mullet (Planiliza haematocheilus) and investigated its role in regulating fish immunity. The open reading frame of PhGal8X1 was 918bp, encoding a soluble protein of 305 amino acids. The protein had a theoretical isoelectric (pI) point of 7.7 and an estimated molecular weight of 34.078 kDa. PhGal8X1 was expressed in various tissues of the fish, with prominent levels in the brain, stomach, and intestine. PhGal8X1 expression was significantly (p < 0.05) induced in the blood and spleen upon challenge with different immune stimuli, including polyinosinic:polycytidylic acid, lipopolysaccharide, and Lactococcus garvieae. The recombinant PhGal8X1 protein demonstrated agglutination activity towards various bacterial pathogens at a minimum effective concentration of 50 μg/mL or 100 μg/mL. Subcellular localization observations revealed that PhGal8X1 was primarily localized in the cytoplasm. PhGal8X1 overexpression in fathead minnow cells significantly (p < 0.05) inhibited viral hemorrhagic septicemia virus (VHSV) replication. The expression levels of four proinflammatory cytokines and two chemokines were significantly (p < 0.05) upregulated in PhGal8X1 overexpressing cells in response to VHSV infection. Furthermore, overexpression of PhGal8X1 exhibited protective effects against oxidative stress induced by H2O2 through the upregulation of antioxidant enzymes. Taken together, these findings provide compelling evidence that PhGal8X1 plays a crucial role in enhancing innate immunity and promoting cell survival through effective regulation of antibacterial, antiviral, and antioxidant defense mechanisms in red-lip mullet.

Molecular characterization and functional analysis of galectin-1 from silver pomfret (Pampus argenteus)

Galectins, as members of lectin families, exhibit a high affinity for β-galactosides and play diverse roles in biological processes. They function as pattern recognition receptors (PRRs) with important roles in immune defense. In this study, galectin-1, designated as SpGal-1, was identified and characterized from silver pomfret (Pampus argenteus). The SpGal-1 comprises an open reading frame (ORF) spanning 396 base pairs (bp) and encodes a deduced amino acid (aa) sequence containing a single carbohydrate recognition domain (CRD). Sublocalization analysis revealed that SpGal-1 was mainly expressed in the cytoplasm. The mRNA transcripts of SpGal-1 were ubiquitously detected in various tissues, with a higher expression level in the intestine. In addition, when exposed to Photobacterium damselae subsp. damselae (PDD) infection, both the liver and head kidney exhibited significantly increased SpGal-1 mRNA expression. The recombinant protein of SpGal-1 (named as rSpGal-1) demonstrated hemagglutination against red blood cells (RBCs) from Larimichthys crocea and P. argenteus in a Ca2+ or β-Mercaptoethanol (β-ME)-independent manner. Notably, rSpGal-1 could bind with various pathogen-associated molecular patterns (PAMPs) including D-galactose, D-mannose, lipopolysaccharide (LPS), and peptidoglycan (PGN), with highest affinity to PGN. Moreover, rSpGal-1 effectively interacted with an array of bacterial types encompassing Gram-positive bacteria (Staphylococcus aureus and Nocardia seriolae) and Gram-negative bacteria (PDD and Escherichia coli, among others), with the most robust binding affinity towards PDD. Collectively, these findings highlight that SpGal-1 is a crucial PRR with involvement in the host immune defense of silver pomfret.

Identification of Galectin 9 and its antibacterial function in yellow drum (Nibea albiflora)

Galectins are a family of evolutionarily conserved lectins that contain carbohydrate recognition domains (CRDs) specifically recognizing β-galactoside. Galectin-9 plays a crucial role in various biological processes during pathogenic infections. In a previous study, galectin-9 was identified as a candidate gene for resistance to Vibrio harveyi disease in yellow drum using a genome-wide association study (GWAS) analysis. In this study, a galectin-9 gene was identified from Nibea albiflora and named YdGal-9. The mRNA transcripts of YdGal-9 were distributed in all the detected tissues and the highest level was found in the kidney. The subcellular localization of YdGal-9-EGFP proteins was observed in both nucleus and cytoplasm in the kidney cells of N. albiflora. The expression of YdGal-9 in the brain increased significantly after infection with Vibrio harveyi. The red blood cells from rabbits, Larimichthys crocea, and N. albiflora were agglutinated by the purified recombinant YdGal-9 proteins. The results of the agglutination activity of deletion mutants of YdGal-9 proved that the conserved sugar binding motifs (H-NPR and WG-EE-) were critical for YdGal-9's agglutination activity. In addition, YdGal-9 killed some gram-negative bacteria by inducing cell wall destruction including Pseudomonas plecoglossicida, Aeromonas hydrophila, Escherichia coli, V. parahemolyticus, V. harveyi, and V. alginolyticus. Taken together, these results suggested that the YdGal-9 protein of N. albiflora played a vital role in fighting bacterial infections.

Genome-wide identification of gap junction (connexins and pannexins) genes in black rockfish (Sebastes schlegelii): Evolution and immune response mechanism following challenge

Cell-to-cell communication through gap junction channels is very important to coordinate the functions of cells in all multicellular biological tissues. It allows the direct exchange of ions and small molecules (including second messengers, such as Ca²⁺, IP3, cyclic nucleotides, and oligonucleotides). In this study, a total of 48 members of the gap junction (GJ) protein family were identified from Sebastes schlegelii. In S. schlegelii, GJ proteins were classified into two types, connexin, and pannexin, and then connexins were divided into five subfamilies. The naming of 48 genes was verified through phylogenetic analysis and syntenic analysis. The connexin proteins contained four transmembrane fragments and two extracellular loops, the lengths of the intracellular loop and C-terminal was quite different, and the C-terminal region was highly variable after post-translational modification. PPI analysis showed that GJs interacted with tight junctions, adhesive junctions, and cell adhesions to form a complex network and participated in cell-cell junction organization, ATP binding, ion channel, voltage-gated conduction, wnt signaling pathway, Fc-γ receptor signaling pathway, and DNA replication. In addition, the S. schlegelii GJ protein was highly expressed in intestinal tissues and remarkably regulated after Edwardsiella tarda and Streptococcus iniae infection. The expression of GJs in intestinal cells of S. schlegelii was significantly regulated by LPS and poly (I:C), which was consistent with the results of intestinal tissue stimulation by pathogens. In conclusion, this study can provide valuable information for further research on the function of S. schlegelii GJ proteins.

An Update of Lectins from Marine Organisms: Characterization, Extraction Methodology, and Potential Biofunctional Applications

Lectins are a unique group of nonimmune carbohydrate-binding proteins or glycoproteins that exhibit specific and reversible carbohydrate-binding activity in a non-catalytic manner. Lectins have diverse sources and are classified according to their origins, such as plant lectins, animal lectins, and fish lectins. Marine organisms including fish, crustaceans, and mollusks produce a myriad of lectins, including rhamnose binding lectins (RBL), fucose-binding lectins (FTL), mannose-binding lectin, galectins, galactose binding lectins, and C-type lectins. The widely used method of extracting lectins from marine samples is a simple two-step process employing a polar salt solution and purification by column chromatography. Lectins exert several immunomodulatory functions, including pathogen recognition, inflammatory reactions, participating in various hemocyte functions (e.g., agglutination), phagocytic reactions, among others. Lectins can also control cell proliferation, protein folding, RNA splicing, and trafficking of molecules. Due to their reported biological and pharmaceutical activities, lectins have attracted the attention of scientists and industries (i.e., food, biomedical, and pharmaceutical industries). Therefore, this review aims to update current information on lectins from marine organisms, their characterization, extraction, and biofunctionalities.

In vivo test of Vibrio alginolyticus and Vibrio harveyi infection in the humpback grouper (Cromileptes altivelis) from East Java Indonesia

Background and Aim:

The need for fish seeds resistant to bacterial and viral infections has encouraged studies on the molecular pathogenesis mechanism of Vibrio bacteria, such as Vibrio alginolyticus and Vibrio harveyi, regarding the receptor organs, protein adhesion mechanisms, and antibody responses of the humpback grouper. This study aims to confirm the characteristics of the specific proteins expressed in the receptor organ of the humpback grouper (Cromileptes altivelis) using the expression of V. alginolyticus and V. harveyi bacteria.

Materials and Methods:

The study was conducted by isolating crude protein and whole cells from both the Vibrio bacteria. In addition, serum and organ tissue were also isolated from fish samples. Then, hemagglutination and dot blot tests with polyacrylamide gel electrophoresis analysis were performed to determine the highest expression of receptor from the whole bacterial cells and crude protein from both healthy and infected (V. alginolyticus and V. harveyi) fishes. Scanning electron microscope results showed that V. alginolyticus and V. harveyi could express bundle-forming pili, which is involved in bacterial autoaggregation and the mediation of the initial attachment of bacteria to their host cells.

Results:

These results indicated that all the specific receptors for protein in fish organs recognized vibriosis antigens. The specificity test showed that the brain, eye, and kidney organs’ receptors provided a quality and quantity level of responses at 22.63, 53.95, and 43.15 kDa, respectively. The polyclonal anti-V. alginolyticus immunoglobulin M (IgM) antibodies were more cross-reactive than the anti-V. harveyi IgM. Hence, this shows that V. alginolyticus bacteria are more pathogenic than V. harveyi.

Conclusion:

In the future, the molecular characteristics of V. alginolyticus and V. harveyi antigens and the specific receptor organ proteins in the humpback grouper can be developed as the basis for constructing molecular peptide-based vaccine materials.

Molecular characterization and antibacterial ability of galectin-3 and galectin-9 in Onychostoma macrolepis

Galectins belong to the β-galactoside binding protein family, which have conserved carbohydrate-recognition domains (CRDs) and participate in innate and acquired immunity in animals. In this study, two galectin genes were cloned from Onychostoma macrolepis, OmGal-3 (galectin-3) and OmGal-9 (galectin-9). The open reading frames (ORFs) of OmGal-3 and OmGal-9 contain 732 and 978 base pairs, encoding 243 and 325 amino acids, respectively. OmGal-3 contains a C-terminal CRD, but OmGal-9 contains an N-terminal CRD and a C-terminal CRD. Two galectins were expressed at varying levels in all tissues examined, with the liver showing the highest expression. The relative gene expression levels of OmGal-3 and OmGal-9 following Aeromonas hydrophila infection were significantly up-regulated in the liver and spleen, and OmGal-9 had a greater increase than OmGal-3. The recombinant OmGal-3 and OmGal-9 proteins (rOmGal-3 and rOmGal-9) were authenticated and verified by SDS-PAGE and western blotting. ROmGal-3 and rOmGal-9 agglutinated all tested bacteria, including 3 g-positive bacteria (Aeromonas hydrophila, Escherichia coli, and Vibrio parahaemolyticus) and 3 g-negative bacteria (Streptococcus agalactiae, Staphylococcus aureus, and Bacillus cereus) in vivo without Ca²⁺. ROmGal-3 showed strong binding both to gram-positive and gram-negative bacteria and OmGal-9 had a stronger binding activity against gram-positive bacteria. Furthermore, rOmGal-3 and rOmGal-9 exhibited dose-dependent binding capability to two classic pathogens associated molecular pattern (LPS and PGN) and two sugars (d-lactose and d-galactose), and rOmGal-3 has better binding activity at lower concentrations in LPS and PGN than rOmGal-3. The integrated analyses indicate that the two galectins probably play an important role in innate immune defense by binding to bacterial cells via the CRD domain against pathogen infection.

Molecular characterization and expression profiling of tandem-repeat galectin-8 from red-spotted grouper (Epinephelus akaara): Potential antibacterial, antiviral, and wound healing activities

Galectin-8 is a typical β-galactoside binding lectin, which primarily functions as a pattern recognition receptor and/or danger receptor that is engaged in pathogen recognition by the host innate immune system. Although several fish galectins have been identified, the role of galectin-8 in teleost immunity is still not fully understood. In this study, molecular, transcriptional, and immune-related functions of galectin-8 (EaGal8) from red-spotted grouper (Epinephelus akaara) were analyzed. The open reading frame of EaGal8 comprised 960 bp encoding 319 amino acids of a ∼35 kDa protein, composed of the N- and C-terminal carbohydrate recognition domains joined by a short hinge peptide. Phylogenetic analysis revealed that EaGal8 was closely related to the Epinephelus lanceolatus galectin-8-like protein. Although EaGal8 showed ubiquitous tissue expression, the highest expression level was observed in the blood. Immunostimulants, including lipopolysaccharide, poly(I:C), and nervous necrosis virus, significantly upregulated the EaGal8 transcription level in a time-dependent manner (p < 0.05). Furthermore, recombinant EaGal8 (rEaGal8) showed a binding affinity toward seven different carbohydrates in a concentration-dependent manner. In addition, rEaGal8 caused strong agglutination of fish red blood cells and several gram-positive and gram-negative bacteria, including Streptococcus iniae, Streptococcus parauberis, Lactococcus garvieae, Escherichia coli, Edwardsiella tarda, Vibrio alginolyticus, Vibrio parahaemolyticus, and Pseudomonas aeruginosa. For the first time in teleosts, we report the wound healing ability of galectin-8 in this study. At low concentrations, rEaGal8 showed potential wound healing responses in FHM cells, in vitro. Thus, this study reinforces the role of EaGal8 in innate immune responses against bacterial and viral infections and wound healing in red-spotted grouper.

Characterization and functional study of a chimera galectin from yellow drum Nibea albiflora

Galectins are protein that participates in a variety of immune responses in the process of pathogenic infections. In the present study, a chimera galectin gene was screened from the transcriptome database of Nibea albiflora, which was named as YdGal-3. The results of qRT-PCR showed that the mRNA transcripts of YdGal-3 were ubiquitously distributed in all the detected tissues. After infection with Vibrio harveyi, the expression of YdGal-3 in liver, spleen, and head kidney increased significantly. Immunohistochemistry showed that YdGal-3 protein was widely expressed in the head kidney. The purified YdGal-3 protein by prokaryotic expression agglutinated red blood cells. Sugar inhibition assay showed that the agglutinating activity of YdGal-3 protein was inhibited by different sugars including lactose, D-galactose, and lipopolysaccharide. In addition, we mutated YdGal-3 His 294 into proline (P), alanine (A), glycine (G), and aspartic acid (D), it was further proved that the residue plays a key role in agglutination. YdGal-3 agglutinated some gram-negative bacteria including Pseudomonas plecoglossicida, Vibrio parahemolyticus, V. harveyi, and Aeromonas hydrophila, and exhibited antibacterial activity. These results suggested that YdGal-3 protein played an important role in the innate immunity of N. albiflora.

Molecular characterization, expression analysis and immune effect of Galectin-8 from Japanese flounder (Paralichthys olivaceus)

Galectin-8 gene belongs to the agglutinin family, which can specifically recognize β-galactoside bonds and play essential roles in many biological processes. In this study, we researched the sequence characteristics and immune-related function of Galectin-8 gene in Japanese flounder Paralichthys olivaceus, named PoGalectin-8. The results showed that the open reading frame of PoGalectin-8 was 891 bp, which encoding a protein with 296 amino acid residues and containing typical HXNPR and WGXEE motifs in the N-terminal and C-terminal CRD domains. Sequence alignment showed that PoGalectin-8 was conserved in different aquatic animals and exhibited the highest similarity (95.27%) with Seriola dumerili. PoGalectin-8 expressed in all detected tissues and exhibited the highest expression level in spleen, followed by skin and kidney. After infected by Edwardsiella tarda, the expression of PoGalectin-8 was down-regulated in the spleen and skin tissues of P. olivaceus. Further to study its immune-related functions, the recombinant PoGalectin-8 (rPoGalectin-8) was expressed and purified. The rPoGalectin-8 can specifically bind to lipopolysaccharide and peptidoglycan, the main components of cell walls from Gram-negative and Gram-positive bacteria. Bacteria binding and the microbial agglutinating experiments showed that the rPoGalectin-8 could bind and agglutinate all examined Gram-positive and Gram-negative bacteria. This study implied that PoGalectin-8, as a pattern recognition receptor, may play important roles during immune responses against bacterial infection, which laid a foundation for further functional identification of Galectin-8 in aquatic animal immunity.

Galectins in turbot (Scophthalmus maximus L.): Characterization and expression profiling in mucosal tissues

Galectins, a family of evolutionary conserved β-galactoside-binding proteins, have been characterized in a wide range of species. Many reports have indicated vital roles of galectins in innate immunity, especially in the mucosal tissues against infection. However, the systematic identification of galectin gene family is still lacking in teleost. Here, we characterized the galectin gene family and investigated their expression profiles post bacterial challenge in turbot (Scophthalmus maximus L.). In this study, a total of 13 galectin genes were characterized in turbot, phylogenetic analyses revealed their strong relationships to half smooth tongue sole and puffer fish, and syntenic analyses confirmed the orthology suggested by the phylogenetic analysis. In addition, the copy number of galectin genes is similar across a broad spectrum of species from fish to amphibians, birds, and mammals, ranging from 8 to 16 genes. Furthermore, the galectin genes were widely expressed in all the examined turbot tissues, and most of the galectin genes were strongly expressed in mucosal tissues (skin, gill and intestine). Moreover, majority of the galectin genes were significantly regulated after Vibrio anguillarum infection in the intestine, gill and skin, suggesting that galectins were involved in the mucosal immune response to V. anguillarum infection in turbot. In addition, subcellular localization analysis showed lgals3a was distributed in the cytoplasm and nucleus. However, the knowledge of galectins are still limited in teleost species, further studies should be carried out to better characterize its detailed roles in teleost mucosal immunity.

Integrated Analysis of circRNA-miRNA-mRNA Regulatory Networks in the Intestine of Sebastes schlegelii Following Edwardsiella tarda Challenge

Sebastes schlegelii, an important aquaculture species, has been widely cultured in East Asian countries. With the increase in the cultivation scale, various diseases have become major threats to the industry. Evidence has shown that non-coding RNAs (ncRNAs) have remarkable functions in the interactions between pathogens and their hosts. However, little is known about the mechanisms of circular RNAs (circRNAs) and coding RNAs in the process of preventing pathogen infection in the intestine in teleosts. In this study, we aimed to uncover the global landscape of mRNAs, circRNAs, and microRNAs (miRNAs) in response to Edwardsiella tarda infection at different time points (0, 2, 6, 12, and 24 h) and to construct regulatory networks for exploring the immune regulatory mechanism in the intestine of S. schlegelii. In total, 1,794 mRNAs, 87 circRNAs, and 79 miRNAs were differentially expressed. The differentially expressed RNAs were quantitatively validated using qRT-PCR. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed that most of the differentially expressed mRNA genes and the target genes of ncRNAs were related to immune signaling pathways, such as the NF-κB signal pathway, pathogen recognition receptors related to signaling pathways (Toll-like receptors and Nod-like receptors), and the chemokine signaling pathway. Based on these differentially expressed genes, 624 circRNA-miRNA pairs and 2,694 miRNA-mRNA pairs were predicted using the miRanda software. Integrated analyses generated 25 circRNA-miRNA-mRNA interaction networks. In a novel_circ_0004195/novel-530/IκB interaction network, novel_530 was upregulated, while its two targets, novel_circ_0004195 and IκB, were downregulated after E. tarda infection. In addition, two circRNA-miRNA-mRNA networks related to apoptosis (novel_circ_0003210/novel_152/apoptosis-stimulating of p53 protein 1) and interleukin (novel_circ_0001907/novel_127/interleukin-1 receptor type 2) were also identified in our study. We thus speculated that the downstream NF-κB signaling pathway, p53 signaling pathway, and apoptosis pathway might play vital roles in the immune response in the intestine of S. schlegelii. This study revealed a landscape of RNAs in the intestine of S. schlegelii during E. tarda infection and provided clues for further study on the immune mechanisms and signaling networks based on the circRNA-miRNA-mRNA axis in S. schlegelii.

Expression and antibacterial analysis of galectin-8 and -9 genes in mandarin fish, Siniperca chuatsi

Galectin-8 and galectin-9 belong to tandem repeat-type galectins, and in the present study, these two genes were cloned in mandarin fish Siniperca chuatsi. The open reading frame (ORF) of the mandarin fish galectin-8 and galectin-9 contains 942, and 1008 bp, encoding 313 and 335 amino acids, respectively. As a conserved feature, an N-terminal carbohydrate recognition domain (CRD), and a C-terminal CRD were observed in each of the two galectins in mandarin fish. In healthy fish, galectin-8 and -9 were constitutively expressed in all organs/tissues examined, and their expression can be induced following the stimulation of LPS and poly(I:C). It is obvious that galectin-8 had a higher increase at mRNA level following the stimulation of poly(I:C). It is further demonstrated that mandarin fish galectin-8 inhibited the growth of Flavobacterium columnare and Streptococcus agalactiae, and in addition to the two species of bacteria, galectin-9 inhibited also the growth of Edwardsiella piscicida, which provides the basis for further understanding their antibacterial role in immune response of mandarin fish.

Transcriptional modifications and the cytoprotective, DNA protective, and wound healing effects of peroxiredoxin-1 from Sebastes schlegelii

Peroxiredoxins are a group of thiol-specific antioxidant proteins that take six isoforms in vertebrates and allow the innate immune system to sense and detoxify reactive oxygen species. In this study, we identified and characterized the perxiredoxin-1 (SsPrdx1) cDNA sequence from the rockfish, Sebastes schlegelii. In silico analysis revealed that SsPrdx1 contained a 594 bp long open reading frame (ORF) encoding a protein of 198 amino acids, with a predicted molecular weight and theoretical isoelectric point of 21.97 kDa and 6.30, respectively. The SsPrdx1 gene comprised six exons linked by five introns, while peroxiredoxin signature motifs were found in the highly conserved third, fourth, and fifth exons. Phylogenetic analysis and sequence alignment suggested that SsPrdx1 is evolutionarily conserved and that its most closely related counterpart is Salarias fasciatus. Recombinant SsPrdx1 (rSsPrdx1) displayed supercoiled DNA protection and insulin disulfide reduction activities in a concentration-dependent manner, while cells transiently transfected with pcDNA3.1 (+)/SsPrdx1 exhibited significant cytoprotective effects under oxidative stress and wound healing activity. SsPrdx1 transcripts were constitutively expressed under normal physiological conditions, with the highest expression observed in the blood. Moreover, SsPrdx1 expression increased in the blood, spleen, and liver following immune provocation by LPS, poly I:C, and Streptococcus iniae injection. Thus, this study provides insights into the role of SsPrdx1 in rockfish immune protection.

Fish Galectin8-Like Exerts Positive Regulation on Immune Response Against Bacterial Infection

Galectin-8 is a member of the galectin family that is involved in immune response against pathogens. However, the roles of fish galectin-8 during pathogen infection require comprehensive studies. In this study, a galectin-8 homolog (OnGal8-like, OnGal8-L) was characterized from Nile tilapia (Oreochromis niloticus), and its roles in response to bacterial infection were analyzed. The OnGal8-L contains an open reading frame of 891 bp, encoding a peptide of 296 amino acids with two CRD regions of tandem-repeat galectin and two carbohydrate recognition sites. The OnGal8-L protein shares 46.42% identities with reported Oreochromis niloticus galectin-8 protein. Transcriptional expression analysis revealed that OnGal8-L was constitutively expressed in all examined tissues and was highly expressed in spleen. The transcript levels of OnGal8-L were up-regulated in the spleen, head kidney, and brain, following Streptococcus agalactiae (S. agalactiae) challenge. Further in vitro analysis indicated that the recombinant protein of OnGal8-L (rOnGal8L) could agglutinate erythrocyte, S. agalactiae, and A. hydrophila and bind S. agalactiae, A. hydrophila, and various PAMPs (lipopolysaccharides, lipoteichoic acid, poly I:C, peptidoglycan, galactose, mannose, and maltose). Also, rOnGal8L could regulate inflammatory-related gene expression, phagocytosis, and a respiratory burst of monocytes/macrophages. Moreover, in vivo analysis showed that OnGal8-L overexpression could protect O. niloticus from S. agalactiae infection through modulating serum antibacterial activity (AKP, ACP, and LZM), antioxidant capacity (CAT, POD, and SOD), and monocyte/macrophage proliferation and cytokine expression, as well as reducing bacterial burden and decreasing tissue damage. Our results collectively indicate that OnGal8-L plays important regulatory roles in immune response against bacterial infection.

Role of rockfish (Sebastes schlegelii) glutaredoxin 1 in innate immunity, and alleviation of cellular oxidative stress: Insights into localization, molecular characteristics, transcription, and function

Glutaredoxins are a group of heat stable oxidoreductases ubiquitously found in prokaryotes and eukaryotes. They are widely known for GSH (glutathione)-dependent protein disulfide reduction and cellular redox homeostasis. This study was performed to identify and characterize rockfish (Sebastes schlegelii) glutaredoxin 1 (SsGrx1) at molecular, transcriptional, and functional levels. The coding sequence of SsGrx1 was 318 bp in length and encoded a protein containing 106 amino acids. The molecular weight and theoretical isoelectric point of the putative SsGrx1 protein were 11.6 kDa and 6.71 kDa, respectively. The amino acid sequence of SsGrx1 comprised a CPYC redox active motif surrounded by several conserved GSH binding sites. The modeled protein structure was found to consist of five α-helices and four β-sheets, similar to human Grx1. SsGrx1 showed a tissue specific expression in all the tissues tested, with the highest expression in the kidney. Immune stimulation by lipopolysaccharides (LPS), polyinosinic:polycytidylic acid (polyI:C), and Streptococcus iniae (S. iniae) could significantly modulate the SsGrx1 expression pattern in the blood and gills. Analysis of its subcellular localization disclosed that SsGrx1 was prominently localized in the cytosol. Recombinant SsGrx1 (rSsGrx1) exhibited significant activity in insulin disulfide reduction assay and HED (β-Hydroxyethyl Disulfide) assay. Furthermore, transient overexpression of SsGrx1 in FHM (fathead minnow) cells significantly enhanced cell survival upon H₂O₂-induced apoptosis. Collectively, our findings strongly suggest that SsGrx1 plays a crucial role in providing rockfish immune protection against pathogens and oxidative stress.

Functional characterization of galectin-3 from Nile tilapia (Oreochromis niloticus) and its regulatory role on monocytes/macrophages

Galectin-3 is a kind of β-galactoside-binding lectin involved in host defense against pathogen infection. However, the immune functions of fish galectin-3 remain poorly understood. In this study, the roles of a fish galectin-3 (OnGal-3) from Nile tilapia (Oreochromis niloticus) on the binding activity on bacterial pathogens or PAMPs, the agglutinating activity on bacterial pathogens and the regulatory effects on monocytes/macrophages activity were investigated. After in vitro challenge of Streptococcus agalactiae and Aeromonas hydrophila, OnGal-3 expressions were significantly up-regulated in monocytes/macrophages. In addition, recombinant OnGal-3(rOnGal-3) protein showed strong binding activity on bacterial pathogens or PAMPs. Also, rOnGal-3 agglutinated Gram-positive and Gram-negative bacteria. Moreover, rOnGal-3 could induce the inflammatory factors expressions in monocytes/macrophages and enhance phagocytosis and respiratory burst activity of monocytes/macrophages. These results suggest that fish galectin-3 participates in anti-bacterial immune response through recognizing pathogens and modulating monocytes/macrophages activity.

Expression analysis of LTR-derived miR-1269a and target gene, KSR2 in Sebastes schlegelii

BACKGROUND

Sebastes schlegelii are an important species of fish found in the coastal areas of the Korea with significant commercial importance. Most studies thus far have been primarily focused on environmental factors; behavioural patterns, aquaculture, diseases and limited genetic studies with little to none related to either microRNAs (miRNAs) or transposable elements (TE).

OBJECTIVES

In order to understand biological roles of TE-derived miR-1269a, we examined expression pattern for miR-1269a and its target gene, KSR2, in various tissues of Sebastes schlegelii. Also, we performed luciferase reporter assay in HINAE cells.

METHODS

UCSC Genome Browser (https://genome.ucsc.edu/) was used to examine which TE is associated with miR-1269a. For the target genes for miR-1269a, the target genes associated with the miRNA were identified using miRDB (http://www.mirdb.org/) and TargetScan 7.1 (http://www.targetscan.org/vert_71/). A two-step miRNA kit, HB miR Multi Assay Kit™ System. I was used for the analysis of TE-derived miRNA expression patterns. The 3'UTR of KSR2 gene was cloned into the psiCHECK-2 vector. Subsequently co-transfected with miR-1269a mimics to HINAE cells for luciferase reporter assay.

RESULTS

MiR-1269a was found to be derived from LTR retrotransposon, MLT2B. LTR-derived miR-1269a was highly expressed in the muscle, liver and gonad tissues of Sebastes schlegelii, but KSR2 revealed high expression in the brain. Co-transfection of KSR2 and miR-1269a mimic to HINAE cells showed high activity of miR-1269a in relation to KSR2.

CONCLUSION

LTR-derived miR-1269a showed enhancer activity with relation to KSR2 in Sebastes schlegelii. The data may be used as a foundation for further investigation regarding correlation of miRNA and target genes in addition to other functional studies of biological significance in Sebastes schlegelii.