Identification and molecular characterization of two liver expressed antimicrobial peptides (LEAPs) in Amur grayling (Thymallus arcticus grubei Dybowski, 1869)

Abstract

Antimicrobial peptides (AMPs) are part of the innate immune response against bacteria. Liver expressed antimicrobial peptides (LEAPs) are one of the most important antimicrobial peptides in fish and belong to a family of cysteine-rich antimicrobial peptides with antimicrobial activity against a variety of pathogens. In this study, we cloned and identified two liver expressed antimicrobial peptides (TaLEAP-1, TaLEAP-2) from Thymallus arcticus grubei, functional studies were performed and the two synthesized TaLEAPs peptides were examined in vitro bacterial inhibition. The results showed that the open reading frame lengths of TaLEAP-1 and TaLEAP-2 were 267 bp and 258 bp, respectively. TaLEAP-1 is a β-sheet polypeptide containing 89 amino acids, and TaLEAP-2 is an α-helix with β-sheet polypeptide containing 85 amino acids. Tissue distribution showed that both TaLEAPs were widely expressed in ten tissues of T. arcticus grubei, with the highest expression in the liver. During the bacterial challenge with Aeromonas salmonicida and Aeromonas hydrophila, two LEAPs genes were differentially expressed. TaLEAP-1 has broad-spectrum antibacterial activity against a variety of bacteria. TaLEAP-1 damages bacteria by disrupting cell membranes, showing that TaLEAP-1 has potent antibacterial effects. Cytotoxicity assay results showed that TaLEAP-1 was not toxic and TaLEAP-2 was slightly toxic to RTG-2. The results of this study provide strategies for resistance to bacterial and fungal infections in T. arcticus grubei.