Cloning, expression and antimicrobial activity of an antimicrobial peptide, epinecidin-1, from the orange-spotted grouper, Epinephelus coioides

Outbreaks of infectious diseases have caused huge losses in the fish culture industry. The production of antimicrobial peptides has been identified as a major defense mechanism against infections. A cDNA encoding an antimicrobial peptide was isolated from the leukocyte cDNA library of orange-spotted grouper, Epinephelus coioides. The predicted 67-amino acid prepropeptide, named epinecidin-1, consists of three domains: a signal peptide of 22 amino acids, a mature peptide of 25 amino acids, and a carboxy-terminal prodomain of 20 amino acids. The epinecidin-1 gene consisted of three introns and four exons. A TATA box and several consensus-binding motifs for transcription factors were found in the proximal region 5′ to the transcription initiation site. A synthetic, amidated mature peptide of epinecidin-1 exhibited high antimicrobial activity against Vibrio parahaemolyticus, Vibrio alginolyticus, Vibrio vulnificus, Pasturella multocida, Morganella morganii, Aeromonas sobrio, Aeromonas hydrophila, Flavobacterium meningosepticum and Escherichia coli DH5α (minimal bactericidal concentration (MBC) < 5 μM). Most of these bacteria are known pathogens in aquaculture. Some fungi, such as Candida albicans and Microsporosis sanis, were also sensitive to this synthetic peptide (MBC < 20 μM). In conclusion, epinecidin-1 may be effective in the treatment or prevention of bacterial infections in aquaculture, and it may be a candidate gene for the generation of transgenic fish to improve disease resistance in aquaculture.