Antimicrobial activity of histone-derived peptides H2A and H4 from silver pomfret (Pampus argenteus) against Photobacterium damselae subsp. damselae

Abstract

The silver pomfret (Pampus argenteus) is a commercially valuable marine fish species in China. Photobacterium damselae subsp. damselae (PDD) is an opportunistic pathogen in aquaculture environments and has become a serious bacterial pathogen of the aquacultural industry in recent years. In this study, two functional fragments originated from histone-derived peptides (H2A and H4) of the silver pomfret, and were identified and designated as spH2A.2 and spH4. In addition, the full-length cDNA of H2A from silver pomfret (SPH2A) consists of 387 base pairs (bp) coding sequence (CDS) that encodes 128 amino acids (aa), while the full-length cDNA of SPH4 consists of 312 bp CDS and encodes 103 aa. Tissue distribution analysis showed that SPH2A had a higher expression pattern in the head kidney and intestine, while SPH4 was mainly expressed in the spleen. After PDD infection, both histone gene expression levels were significant upregulated at 1 day post-infection (dpi) (P < 0.01) in the liver. Furthermore, spH4 and spH2A.2 peptides had potent antimicrobial activity against Gram-negative bacteria, with the MIC value ranging from 24 to 95 µM and 66–133 µM, respectively. Cytotoxicity of spH4 and spH2A.2 was tested in silver pomfret primary cells (liver, spleen and head kidney), and the results showed that spH4 had no cytotoxicity, while spH2A.2 displayed cytotoxic activity on silver pomfret cells. Additionally, scanning electronic microscope (SEM) analysis revealed that spH4 and spH2A.2 could destroy the PDD cell wall structure. Overall, the spH4 and spH2A.2 peptides were likely prone to exert the antimicrobial activity and may be useful to defend against PDD in silver pomfret aquaculture.

Keywords

• Silver pomfret
• Photobacterium damselae subsp. damselae
• Histone-derived peptide
• Antimicrobial activity
• Disease