title: Comparative cytogenetic mapping of rRNA genes among naked catfishes: implications for genomic evolution in the Bagridae family.
abstract: In the present study, the karyotype and chromosomal characteristics of 9 species of the Bagridae fish family were investigated using conventional Giemsa staining as well as dual-color fluorescence in situ hybridization to detect the 18S and 5S rDNA sites. In addition to describing the karyotype of several Bagridae catfishes, we established molecular cytogenetic techniques to study this group. The 9 species contained a diploid chromosomal number, varying from 50 (Pseudomystus siamensis) to 62 (Hemibagrus wyckii), while none contained heteromorphic sex chromosomes. 18S rDNA sites were detected in only 1 chromosomal pair among all species evaluated. However, 3 different patterns were observed for the distribution of the 5S rDNA: 2 sites were found in the genus Mystus and in P. siamensis, multiple sites were observed in the genus Hemibagrus, and a syntenic condition for the 18S and 5S rDNA sites was identified in H. wyckii. The extensive variation in the number and chromosomal position of rDNA clusters observed among these Bagridae species may be related to the intense evolutionary dynamics of rDNA-repeated units, which generates divergent chromosomal distribution patterns even among closely related species. In summary, the distribution of repetitive DNA sequences provided novel, useful information regarding the evolutionary relationships between Bagridae fishes.
authors.affiliation: Jena University Hospital, Friedrich Schiller University, Institute of Human Genetics, Jena, Germany.
authors.forename: W
authors.initials: W
authors.lastname: Supiwong
authors.affiliation: Jena University Hospital, Friedrich Schiller University, Institute of Human Genetics, Jena, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Liehr
authors.affiliation: Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos, SP, Brasil.
authors.forename: M B
authors.initials: MB
authors.lastname: Cioffi
authors.affiliation: Department of Biology, Faculty of Science, Khon Kaen University, Muangkhonkaen District, Khon Kaen, Thailand raccha@kku.ac.th.
authors.forename: A
authors.initials: A
authors.lastname: Chaveerach
authors.affiliation: Jena University Hospital, Friedrich Schiller University, Institute of Human Genetics, Jena, Germany.
authors.forename: N
authors.initials: N
authors.lastname: Kosyakova
authors.affiliation: Jena University Hospital, Friedrich Schiller University, Institute of Human Genetics, Jena, Germany.
authors.forename: X
authors.initials: X
authors.lastname: Fan
authors.affiliation: Faculty of Environment and Resource Studies, Mahasarakham University, Kantarawichai District, Mahasarakham, Thailand.
authors.forename: T
authors.initials: T
authors.lastname: Tanee
authors.affiliation: Department of Biology, Faculty of Science, Khon Kaen University, Muangkhonkaen District, Khon Kaen, Thailand.
authors.forename: A
authors.initials: A
authors.lastname: Tanomtong
mesh_terms: D000818:Animals; D001483:Base Sequence; D002397:Catfishes / Q000235:genetics*; D002875:Chromosomes / Q000235:genetics; D020732:Cytogenetic Analysis; D004171:Diploidy; D019143:Evolution, Molecular; D020459:Genes, rRNA; D016678:Genome / Q000235:genetics*; D005843:Geography; D017404:In Situ Hybridization, Fluorescence; D007621:Karyotyping; D020161:Physical Chromosome Mapping; D012337:RNA, Ribosomal, 18S / Q000235:genetics; D012341:RNA, Ribosomal, 5S / Q000235:genetics; D018401:Sample Size; D013785:Thailand
chemical_list: D012337:RNA, Ribosomal, 18S; D012341:RNA, Ribosomal, 5S