We isolated a novel 22-residue, C-terminally amidated antimicrobial peptide, moronecidin, from the skin and gill of hybrid striped bass. Two isoforms, differing by only one amino acid, are derived from each parental species, white bass (Morone chrysops) and striped bass (Morone saxatilis). Molecular masses (2543 and 2571 Da), amino acid sequences (FFHHIFRGIVHVGKTIH(K/R) LVTGT), cDNA, and genomic DNA sequences were determined for each isoform. A predicted 79-residue moronecidin prepropeptide consists of three domains: a signal peptide (22 amino acids), a mature peptide (22 amino acids), and a C-terminal prodomain (35 amino acids). The synthetic, amidated white bass moronecidin exhibited broad spectrum antimicrobial activity that was retained at high salt concentration. An ␣-helical structure was confirmed by circular dichroism spectroscopy. The moronecidin gene consists of three introns and four exons. Peptide sequence and gene organization were similar to pleurocidin, an antimicrobial peptide from winter flounder. A TATA box and several consensus-binding motifs for transcription factors were found in the region 5 to the transcriptional start site. Moronecidin gene expression was detected in gill, skin, intestine, spleen, anterior kidney, and blood cells by kinetic reverse transcription (RT)-PCR. Thus, moronecidin is a new ␣-helical, broad spectrum antimicrobial peptide isolated from the skin and gills of hybrid striped bass.

We report the isolation of a novel antimicrobial peptide, bass hepcidin, from the gill of hybrid striped bass, white bass (Morone chrysops) · striped bass (M. saxatilis). After the intraperitoneal injection of Micrococcus luteus and Escherichia coli, the peptide was purified from HPLC fractions with antimicrobial activity against Escherichia coli. Sequencing by Edman degradation revealed a 21-residue peptide (GCRFCCNCCPNMSGCGVCCRF) with eight putative cysteines. Molecular mass measurements of the native peptide and the reduced and alkylated peptide confirmed the sequence with four intramolecular disulfide bridges. Peptide sequence homology to human hepcidin and other predicted hepcidins, indicated that the peptide is a new member of the hepcidin family. Nucleotide sequences for cDNA and genomic DNA were determined for white bass. A predicted prepropeptide (85 amino acids) consists of three domains: a signal peptide (24 amino acids), prodomain (40 amino acids) and a mature peptide (21 amino acids). The gene has two introns and three exons. A TATA box and several consensus-binding motifs for transcription factors including C/EBP, nuclear factor-jB, and hepatocyte nuclear factor were found in the region upstream of the transcriptional start site. In white bass liver, hepcidin gene expression was induced 4500-fold following challenge with the fish pathogen, Streptococcus iniae, while expression levels remained low in all other tissues tested. A novel antimicrobial peptide from the gill, bass hepcidin, is predominantly expressed in the liver and highly inducible by bacterial exposure.Keywords: antimicrobial peptide; fish; hepcidin; innate immunity; Streptococcus iniae.Antimicrobial peptides (AMPs) are a broadly distributed group of molecules that are important in host defense against microbial invasion. A growing number of peptides involved in innate immunity have been isolated from plants, invertebrates, and higher vertebrates. Human hepcidin and liver-expressed antimicrobial peptide (LEAP-1) are identical AMPs, which were isolated independently from urine and human blood ultrafiltrate, respectively [1,2]. Peptide sequences of additional hepcidins have been predicted from expressed sequence tag databases from the liver of mouse Fish have evolved to thrive in an aqueous environment with a rich microbial flora, and several AMPs have been isolated from fish [7]. During our search for AMPs from gills of hybrid striped bass, three RP-HPLC fractions with antimicrobial acitivity were found [8]. One contained moronecidin, a 22-residue AMP with an amphipathic a-helical structure. From two other adjacent fractions, we isolated another novel AMP, bass hepcidin, a 21-residue, cysteine-rich peptide, which is a homologue of human hepcidin. We report here the first hepcidin to be isolated from a nonhuman vertebrate, the first cysteine-rich AMP isolated from fish, and the first demonstration of hepcidin gene expression induced by live bacterial challenge. M A T E R I A L S A N D M E T H O D STissue collection and purification of ba...

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The objective of this study was to describe the organization of schools of the pelagic marine fishes Scomber japonicus, Trachurus symmetricus, Engraulis mordax, Atherinopsis californiensis, and Atherinops affinis. Organization was studied in larval through adult stages by analysis of spatial and angular relations among fish in dorsal photographs of schools.In all species, schools of young fish, larval and juveniles, were typically less compact and showed greater differences in angular headings than did schools of adult fish. The rate at which school structure changed with size varied among species; it was rapid in Scomber and the atherinids and slower in Engraulis and Trachurus. School organization differed among species at the adult stage. Schools of Scomber were typically the most compact and organized; Trachurus and Engraulis schools were intermediate in their organization and Atherinops schools were the least organized.Spatial and angular measurements were also used to develop inferences regarding the "following reaction" in four of the species. The similarity in angular headings between fish was used as the criterion of following. These analyses showed that the similarities in headings between two fish in a school decreased with the distance they were apart. The headings most alike between adjacent fish in a school were between those in file. These results suggested that the neighbor directly ahead of a given fish in a school is used more frequently as an angular reference for the following reaction than ones to the side.Analysis of the distances between neighbors in the four species indicated that fish were closer to adjacent neighbors in the file than they were to ones in rank. This suggested that spacing in the horizontal plane might be related to tail movement.

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