Even though defensins are important components of the immune system of multicellular organisms, their presence in teleosts have received scant attention. In response, these animals secrete a wide range of AMPs and AMPPs as part of their defence mechanism,. īony fish are the most diverse group of vertebrates and they live in a complex aquatic environment, where they are exposed to water-borne pathogens and deeply affected by abiotic factors. They are involved in host-microbiota interaction, immunomodulation through chemotaxis of immune cells and serve as potential links between innate and adaptive immunity. ![]() In addition to their antimicrobial activity, animal defensins have other known biological roles. These cationic AMPs with a β-sheet structure stabilised by disulphide bridges are widely distributed across both plant and animal kingdoms. These findings imply that beta-defensins may play an important role in the innate immune response of Atlantic cod.ĭefensins are important components of the innate arsenal of antimicrobial peptides (AMPs) and proteins (AMPPs) that provide protection against potential pathogens. In addition, Defb stimulated phagocytic activity of cod head kidney leucocytes in vitro. Recombinant Defb displayed antibacterial activity, with a minimal inhibitory concentration of 0.4–0.8 µM and 25–50 µM against the Gram-(+) bacteria Planococcus citreus and Micrococcus luteus, respectively. Defb was differentially expressed in several tissues following antigenic challenge with Vibrio anguillarum, being up-regulated up to 25-fold in head kidney. During embryonic development, defb gene transcripts were detectable from the golden eye stage onwards and their expression was restricted to the swim bladder and retina. In situ hybridisation revealed that defb was specifically expressed by cells located in the swim bladder submucosa and the oocytes. RT-PCR analysis indicated that defb transcripts were present mainly in the swim bladder and peritoneum wall but could also be detected at moderate to low levels in skin, head- and excretory kidneys. ![]() The tertiary structure of Defb exhibits an α/β fold with one α helix and β 1β 2β 3 sheets. This pattern is typical of beta-defensins and this gene was therefore named cod beta-defensin ( defb). The mature cod defensin has six conserved cysteine residues that form 1–5, 2–4 and 3–6 disulphide bridges. ![]() This three exon/two intron defensin gene codes for a peptide precursor consisting of two domains: a signal peptide of 26 amino acids and a mature peptide of 40 residues. A novel defensin antimicrobial peptide gene was identified in Atlantic cod, Gadus morhua.
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