title: NK-lysin of channel catfish: gene triplication, sequence variation, and expression analysis.
abstract: Antimicrobial peptides (AMPs) are important components of the host innate immune response against microbial invasion. In addition to the previously known four classes of antimicrobial peptides, a fifth class of antimicrobial peptides has been recently identified to include NK-lysins that have a globular three-dimensional structure and are larger with 74-78 amino acid residues. NK-lysin has been shown to harbor antimicrobial activities against a wide spectrum of microorganisms including bacteria, fungi, protozoa, and parasites. To date, NK-lysin genes have been reported from only a limited number of organisms. We previously identified a NK-lysin cDNA in channel catfish. Here we report the identification of two novel types of NK-lysin transcripts in channel catfish. Altogether, three distinct NK-lysin transcripts exist in channel catfish. In this work, their encoding genes were identified, sequenced, and characterized. We provide strong evidence that the catfish NK-lysin gene is tripled in the same genomic neighborhood. All three catfish NK-lysin genes are present in the same genomic region and are tightly linked on the same chromosome, as the same BAC clones harbor all three copies of the NK-lysin genes. All three NK-lysin genes are expressed, but exhibit distinct expression profiles in various tissues. In spite of the existence of a single copy of NK-lysin gene in the human genome, and only a single hit from the pufferfish genome, there are two tripled clusters of NK-lysin genes on chromosome 17 of zebrafish in addition to one more copy on its chromosome 5. The similarity in the genomic arrangement of the tripled NK-lysin genes in channel catfish and zebrafish suggest similar evolution of NK-lysin genes.
authors.affiliation: The Fish Molecular Genetics and Biotechnology Laboratory, Department of Fisheries and Allied Aquacultures and Program of Cell and Molecular Biosciences, Aquatic Genomics Unit, Auburn University, 203 Swingle Hall, Auburn, AL 36849, USA.
authors.forename: Qun
authors.initials: Q
authors.lastname: Wang
authors.forename: Yaping
authors.initials: Y
authors.lastname: Wang
authors.forename: Peng
authors.initials: P
authors.lastname: Xu
authors.forename: Zhanjiang
authors.initials: Z
authors.lastname: Liu
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D005784:Gene Amplification; D018628:Gene Dosage; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D023061:Gene Order; D016678:Genome / Q000235:genetics; D007059:Ictaluridae / Q000235:genetics* / Q000276:immunology*; D007113:Immunity, Innate / Q000235:genetics; D008969:Molecular Sequence Data; D011510:Proteolipids / Q000235:genetics*; D017422:Sequence Analysis, DNA; D014158:Transcription, Genetic
chemical_list: C093238:NK-lysin; D011510:Proteolipids