Cloning and developmental expression of a family of pleurocidin-like antimicrobial peptides from winter flounder, Pleuronectes americanus (Walbaum)

Low molecular weight antimicrobial peptides are an important component of t he innate immune system in animals, yet they have not been examined widely in fish. Of particular interest is their expression during development and in response to environmental conditions and disease. Here, we report the is olation of four genomic sequences encoding putative antimicrobial peptides from the winter flounder, Pleuronectes americanus Walbaum), as well as reve rse transcription-PCR products from two tissues that form the first defensi ve barrier to microbes - skin and intestine. Alignment of the predicted pol ypeptide sequences shows a conserved hydrophobic signal peptide of 22 amino acids followed by 25 amino acids that are identical (WF2) or homologous to the amino acid sequence of pleurocidin, followed by a conserved acidic por tion. Southern hybridisation analysis indicates that related peptides are e ncoded in the genomes of other flatfish species. Northern and RT-PCR analys es of RNA from multiple tissues show that two of the pleurocidin genes are expressed predominantly in the skin whereas two other genes are expressed m ainly in the intestine. RT-PCR assays of total RNA from larvae of different ages provide the first evidence of developmental expression of antimicrobi al peptides in fish and indicate that the pleurocidin gene is first express ed at 13 days post-hatch in winter flounder. Crown Copyright (C) 2000 Publi shed by Elsevier Science Ltd. Ail rights reserved.