Molecular Characterization and Antimicrobial Immune Function Analysis of Hepcidin Genes in Silver Pomfret (Pampus Argenteus)

Abstract

Hepcidins are a group of cysteine rich antimicrobial peptides, which play an important role in fish response to a variety of pathogens. In this study, two hepcidins were identified from silver pomfret (Pampus argenteus), named Pahepcidin1 and Pahepcidin2. Our results showed that Pahepcidin1 contained a 267 open reading frame (ORF) encoding 91 amino acids, while Pahepcidin2 contained 246 bp ORF encoding 81 amino acids. Sequence comparison of Pahepcidins with other homologous genes showed that there were eight conserved cysteines in the mature peptide region of Pahepcidin1 and six cysteine residues in the C-terminus region of Pahepcidin2. Phylogenetic analysis indicated that Pahepcidin1 and Pahepcidin2 were clustered together with other fish homologues, respectively. Tissue-specific expression analysis revealed that the highest expression of Pahepcidins was observed in liver, and the expression of Pahepcidin1 in silver pomfret liver cells significantly increased after Lipopolysaccharide (LPS) and polyinosinic-polycytidylic acid (poly I:C) infection. Then the antibacterial function of recombinant Pahepcidin1 was verified, demonstrating extensive antibacterial activity against both Gram-positive (Staphylococcus aureus) and Gram-negative (Edwardsiella tarda) bacteria. Besides, the overexpression of Pahepcidin1 could markedly alter the transcription levels of the key genes for NF-κB pathway activation and the downstream immunity-related genes. These results indicated that Pahepcidin1 might play a significant role in the innate immune system modulation of silver pomfret, providing important reference for understanding the antimicrobial immune mechanism of this species.

Keywords: Silver pomfret, Hepcidin, Antimicrobial peptide