title: Molecular characterization and expression analysis of the channel catfish cathepsin D genes.
abstract: Cathepsin D is a lysosomal aspartic proteinase that participates in various degradation functions of the cell. In this study, we characterized the cathepsin D genes in channel catfish and found two genes encoding catfish cathepsin D, referred to as cathepsin D1 and D2 genes. These two genes are highly similar in genomic structure and organization, sharing a moderate level of amino acid sequence similarity (56%). Genomic Southern analysis suggested the presence of a single copy of each of the cathepsin D1 and D2 genes. Phylogenetic analysis provided strong evidence that two cathepsin D genes are present in most of the teleost lineage, with cathepsin D2 likely having been lost in some higher vertebrate lineages. The catfish cathepsin D1 and D2 genes are expressed in virtually all the 11 tested tissues (brain, gill, heart, head kidney, trunk kidney, intestine, liver, muscle, skin, spleen, and stomach) on the transcript level, but appear to exhibit greater levels of expression in immune-related tissues and organs. Upon infection with Edwardsiella ictaluri, the expression of the catfish cathepsin D genes showed the most significant changes in liver and head kidney, with time points and magnitude of transcript changes varying between the two genes. We additionally examined bacterially-mediated changes of expression in gill, intestine, and trunk kidney. The fact that bacterial infection can induce expression of the cathepsin D genes and that they appeared to be expressed naturally at higher levels in immune-related organs may suggest that they are an important component of the innate immune response of catfish against bacterial infections.
authors.affiliation: College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi 712100, China.
authors.forename: Tingting
authors.initials: T
authors.lastname: Feng
authors.forename: Hao
authors.initials: H
authors.lastname: Zhang
authors.forename: Hong
authors.initials: H
authors.lastname: Liu
authors.forename: Zunchun
authors.initials: Z
authors.lastname: Zhou
authors.forename: Donghong
authors.initials: D
authors.lastname: Niu
authors.forename: Lilian
authors.initials: L
authors.lastname: Wong
authors.forename: Huseyin
authors.initials: H
authors.lastname: Kucuktas
authors.forename: Xiaolin
authors.initials: X
authors.lastname: Liu
authors.forename: Eric
authors.initials: E
authors.lastname: Peatman
authors.forename: Zhanjiang
authors.initials: Z
authors.lastname: Liu
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002402:Cathepsin D / Q000235:genetics*; D018076:DNA, Complementary / Q000235:genetics; D020610:Edwardsiella ictaluri / Q000502:physiology*; D004756:Enterobacteriaceae Infections / Q000276:immunology / Q000662:veterinary*; D005393:Fish Diseases / Q000276:immunology* / Q000382:microbiology; D029941:Fish Proteins / Q000235:genetics*; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D007059:Ictaluridae / Q000145:classification / Q000235:genetics* / Q000276:immunology; D007113:Immunity, Innate; D008969:Molecular Sequence Data; D010802:Phylogeny; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
chemical_list: D018076:DNA, Complementary; D029941:Fish Proteins; D002402:Cathepsin D