title: Karyotype and cytogenetic mapping of 9 classes of repetitive DNAs in the genome of the naked catfish Mystus bocourti (Siluriformes, Bagridae).
abstract: BACKGROUND
  In the present study, conventional and molecular cytogenetic studies were performed in the naked catfish Mystus bocourti (Siluriformes, Bagridae). Besides the conventional Giemsa staining, fluorescence in situ hybridization (FISH) using nine classes of repetitive DNAs namely 5S and 18S rDNAs, U2 snRNA, the microsatellites (CA)15 and (GA)15, telomeric repeats, and the retrotransposable elements Rex1, 3 and 6. was also performed.
  
  
  RESULTS
  M. bocourti had 2n = 56 chromosomes with a karyotype composed by 11 m + 11 sm + 6 st/a and a fundamental number (NF) equal to 100 in both sexes. Heteromorphic sex chromosome cannot be identified. The U2 snRNA, 5S and 18S rDNA were present in only one pair of chromosomes but none of them in a syntenic position. Microsatellites (CA)15 and (GA)15 showed hybridization signals at subtelomeric regions of all chromosomes with a stronger accumulation into one specific chromosomal pair. FISH with the telomeric probe revealed hybridization signals on each telomere of all chromosomes and interstitial telomeric sites (ITS) were not detected. The retrotransposable elements Rex1, 3 and 6 were generally spread throughout the genome.
  
  
  CONCLUSIONS
  In general, the repetitive sequences were not randomly distributed in the genome, suggesting a pattern of compartmentalization on the heterochromatic region of the chromosomes. Little is known about the structure and organization of bagrid genomes and the knowledge of the chromosomal distribution of repetitive DNA sequences in M. bocourti represents the first step for achieving an integrated view of their genomes.
authors.affiliation: Department of Biology Faculty of Science, Khon Kaen University, 123 Mitraphap Highway, Khon Kaen 40002, Muangkhonkaen District, Thailand. raccha@kku.ac.th.
authors.forename: Weerayuth
authors.initials: W
authors.lastname: Supiwong
authors.forename: Thomas
authors.initials: T
authors.lastname: Liehr
authors.forename: Marcelo B
authors.initials: MB
authors.lastname: Cioffi
authors.forename: Arunrat
authors.initials: A
authors.lastname: Chaveerach
authors.forename: Nadezda
authors.initials: N
authors.lastname: Kosyakova
authors.forename: Krit
authors.initials: K
authors.lastname: Pinthong
authors.forename: Tawatchai
authors.initials: T
authors.lastname: Tanee
authors.forename: Alongklod
authors.initials: A
authors.lastname: Tanomtong