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C-type lectins (CTL) are a large group of pattern-recognition proteins and to play important roles in glycoprotein metabolism, multicellular integration, and immunity. Based on their overall domain structure, they can be classified as different groups that possess different physiological functions. A typical C-type lectin (named as Om Lec1) was identified from the fish, Onychostoma macrolepis , an important cultured fish in China. Open reading frame of Om Lec1 contains a 570 bp, encoding a protein of 189 amino acids that includes a signal peptide and a single carbohydrate-recognition domain. The phylogenetic analysis showed that Om Lec1 could be grouped with C-type lectin from other fish. Om Lec1 was expressed in all the tissues in our study, and the expression level was highest in liver. And its relative expression levels were significantly upregulated following infection with Aeromonas hydrophila. The recombinant Om Lec1 protein (r Om Lec1) could agglutinate some Gram-negative bacteria and Gram-positive bacteria in vitro in the presence of Ca2+, showing a typical Ca2+-dependent carbohydrate-binding protein. Furthermore, r Om Lec1 purified from E. coli BL21 (DE3), strongly bound to LPS and PGN, as well as all tested bacteria in a Ca2+-dependent manner. These results indicate that Om Lec1 plays a central role in the innate immune response and as a pattern recognition receptor that recognizes diverse pathogens among O. macrolepis. • A typical C-type lectin with a EPN/WND motif (Om Lec1) was identified and characterized from Onychostoma macrolepis. • The expression levels of Om Lec1 gene were significantly up-regulated after pathogen challenge. • Recombinant Om Lec1 can agglutinates various bacteria in vitro in the presence of Ca2+. • Recombinant Om Lec1 could bind some saccharides such as d -mannose, LPS and PGN. [ABSTRACT FROM AUTHOR]

• A novel C-type lectin with a EPN/WND motif (OmCTL) was identified and characterized from Onychostoma macrolepis. • The expression levels of OmCTL gene were significantly upregulated after pathogen challenge. • Recombinant OmCTL can agglutinates various bacteria in vitro in the presence of Ca2+. • Recombinant OmCTL could bind some saccharides such as d-mannose, LPS and PGN and so on. C-type lectins (CTLs) are calcium-dependent carbohydrate-binding proteins that mainly bind to carbohydrate-based or other ligands to mediate cell adhesion, recognize pathogens, and play important roles in the immune system. In the present study, a novel C-type lectin (OmCTL) isolated from Onychostoma macrolepis was investigated. The open reading frame of OmCTL comprises 468 bp, encoding a 155 amino acid polypeptide with an 18 amino acid putative signaling peptide. The predicted primary OmCTL structure contains a signal peptide, a single carbohydrate recognition domain (CRD) and an EPN/WND motif required for carbohydrate-binding specificity. Using tissue expression pattern analysis, OmCTL has been shownto be highly expressed in the liver, and is also detected in other tissues. OmCTL was significantly upregulated in the liver and spleen following infection with Aeromonas hydrophila , suggesting its involvement in immune response. The recombinant OmCTL protein (rOmCTL) agglutinated two gram-negative bacteria, Escherichia coli and A. hydrophila , in vitro in the presence of Ca2+, showing that it is a typical Ca2+-dependent carbohydrate-binding protein.Furthermore, rOmCTL purified from E. coli BL21 (DE3) strongly bound to LPS and PGN, as well as all tested bacteria in a Ca2+-independent manner. These results indicate that OmCTL plays a central role in the innate immune response and as a pattern recognition receptor that recognizes diverse pathogens among O. macrolepis. [ABSTRACT FROM AUTHOR]

C-type lectins (CTLs), a superfamily of Ca2+-dependent carbohydrate-recognition proteins, serve as pattern recognition receptors (PRRs) in the immune response of many species. However, little is currently known about the CTLs of the commercially and ecologically important bivalve species, blood clam (Tegillarca granosa). In this study, a CTL (designated as Tg CTL-1) with a single carbohydrate-recognition domain (CRD) containing unique QPN/WDD motifs was identified in the blood clam through transcriptome and whole-genome searching. Multiple alignment and phylogenetic analysis strongly suggested that Tg CTL-1 was a new member of the CTL superfamily. Expression analysis demonstrated that TgCTL-1 was highly expressed in the hemocytes and visceral mass of the clam under normal condition. In addition, the expression of TgCTL-1 was shown to be significantly up-regulated upon pathogen challenge. Moreover, the recombinant Tg CTL-1 (r Tg CTL-1) displayed agglutinating and binding activities against both the gram-positive and gram-negative bacteria tested in a Ca2+-dependent manner. Furthermore, it was found that the in vitro phagocytic activity of hemocytes was significantly enhanced by r Tg CTL-1. In general, our results showed that Tg CTL-1 was an inducible acute-phase secretory protein, playing crucial roles in recognizing, agglutinating, and binding to pathogenic bacteria as well as modulating phagocytic activity of hemocytes in the innate immune defense of blood clam. • A novel C-type lectin, TgCTL-1 , was identified in blood clam, T. granosa. • TgCTL- 1 has a single carbohydrate-recognition domain (CRD) containing QPN/WDD motifs. • Expression of TgCTL-1 was rapidly and markedly up-regulated upon pathogen challenge. • The r Tg CTL-1 exhibited binding and agglutinating activities in a Ca+-dependent manner. • r Tg CTL-1 was shown to promote phagocytic activity of hemocytes especially with Ca2+. [ABSTRACT FROM AUTHOR]

C-type lectins (CTLs) have characteristic carbohydrate recognition domains (CRDs) and play important roles in the immune system. In the present study, a new CTL, Sp CTL5, was identified from the hepatopancreas of the mud crab Scylla paramamosain. The open reading frame of Sp CTL5 comprised 762 bp, encoding a polypeptide of 253 amino acids with a putative signaling peptide of 20 amino acids. The predicted Sp CTL5 protein contained a single CRD. Sp CTL5 transcripts were distributed in all examined tissues, with the highest level being detected in the hepatopancreas. Upon challenging with Vibrio alginolyticus , the mRNA levels of Sp CTL5 in the hepatopancreas were up-regulated. The recombinant protein of Sp CTL5 could agglutinate three Gram-positive bacteria and three Gram-negative bacteria in the presence of Ca2+. Furthermore, hemagglutination analysis showed that the recombinant protein of Sp CTL5 can agglutinate rabbit erythrocytes. This study indicated that Sp CTL5 acts as a pattern recognition receptor for the innate immune response which protects S. paramamosain from bacterial infection. Moreover, these findings also provide information to further our understanding of the innate immunology of invertebrates. • Sp CTL5 might be involved in the innate immune response. • Sp CTL5 can agglutinate Gram-positive and Gram-negative bacteria. • Sp CTL5 acts as a pattern recognition receptor with Ca2+ dependently. [ABSTRACT FROM AUTHOR]