Sammendrag
Atlantic cod (Gadus morhua), akin to other teleosts, is thought to rely heavily on its innate immune system for protection against microbial exploitation. This includes antimicrobial peptides that play a crucial role in host defence against invading microorganisms. In this first report from a basal teleost (Paracanthopterygii), we identified a piscidin gene in Atlantic cod adopting an in silico approach. This gene, comprising two introns and three exons, was found to be under positive selection, suggesting its possible role in adaptation to new environments or evolving pathogens. The predicted mature cod piscidin contains 22 residues, including the four conserved histidines typical of piscidins and its sequence shows very high similarity with piscidins from other fish species. Further studies found that cod piscidin is constitutively expressed in several tissues (primarily in gut, head kidney, spleen and gills) of naive fish and also during early developmental stages. We also noted expression changes at the mRNA level after the fish were challenged with heat-killed bacteria. Thus piscidins are ancient defence factors and this peptide in Atlantic cod is likely to be involved in its innate immune response against invading pathogens.
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