Molecular characterization and expression analysis of a novel C-type lectin (CTL) gene in yellow catfish Pelteobagrus fulvidraco

C-type lectin (CTL) proteins contain special carbohydrate-recognition domains (CRDs) and play vital roles in activating the innate immune system. In this study, a CTL gene from freshwater yellow catfish (Pelteobagrus fulvidraco) was identified and named as PfCTL. Analysis revealed that the complete PfCTL cDNA was 718 bp in size, including a 42-bp 5 '-untranslated region (UTR), 61-bp 3 '-UTR, and 615-bp open reading frame (ORF) encoding a 204 amino acid polypeptide, which contained a signal peptide and CRD. The PfCTL protein contained two casein kinase II phosphorylation sites, four protein kinase C phosphorylation sites, and two N-myristoylation sites. The deduced PfCTL protein sequence has 37-83 % in comparison to CTL proteins from other fish. Further phylogenetic analysis revealed that PfCTL was closely related to the CTL of Ictalurus punctatus. Based on quantitative real-time polymerase chain reaction, the PfCTL gene was expressed in all tested tissues at different levels, with highest distribution in the spleen, followed by the head kidney, and lowest distribution in blood. After challenge with lipopolysaccharide and polyriboinosinic polyribocytidylic acid, the expression of PfCTL was upregulated in the liver, spleen, head kidney, and blood at different time points. These results imply that this CTL gene may be an important pathogen pattern recognition molecule in the innate immune system of yellow catfish under pathogen stimulation.