title: Molecular organization of 5S rDNA in bitterlings (Cyprinidae).
abstract: Molecular organization and nucleotide sequences of the 5S rRNA gene and NTS were investigated in freshwater fish, bitterlings (Acheilognathinae), including 10 species/subspecies of four genera, Acheilognathus, Pseudoperilampus, Rhodeus, and Tanakia, to understand the evolutionary trait of 5S rDNA arrays. Southern hybridization analysis revealed a general trend with tandem repeats of 5S rDNA in all the examined bitterlings. Sequence analysis demonstrated a conserved 120 bp sequence of the 5S rRNA gene and a short NTS of 56-67 bp with two distinct portions, a conserved (5'-flanking portion; at positions -1 to -38) and a variable part (3'-flanking portion), in 6 of 10 species/subspecies examined. The conserved NTS region was most likely an external promoter so far observed in various vertebrates, whereas the variable NTS region could be divided into two types due to its nucleotide polymorphisms. Molecular phylogeny using the 5S rRNA gene and NTS sequences suggested the occurrence of 5S rDNA duplication before speciation and a concerted evolution for the gene and conserved NTS regions, but a birth-and-death process to maintain the variable NTS region. Thus, the 5S rDNA in the examined bitterlings might have evolved under a mixed process of evolution.
authors.affiliation: Department of Biology, Faculty of Science, Toho University, Miyama 2-2-1, Funabashi, Chiba, 274-8510, Japan.
authors.forename: Mika
authors.initials: M
authors.lastname: Fujiwara
authors.forename: Junya
authors.initials: J
authors.lastname: Inafuku
authors.forename: Akiko
authors.initials: A
authors.lastname: Takeda
authors.forename: Akiko
authors.initials: A
authors.lastname: Watanabe
authors.forename: Atushi
authors.initials: A
authors.lastname: Fujiwara
authors.forename: Sei-Ichi
authors.initials: S
authors.lastname: Kohno
authors.forename: Souichirou
authors.initials: S
authors.lastname: Kubota
mesh_terms: D000818:Animals; D001483:Base Sequence; D003530:Cyprinidae / Q000235:genetics*; D004275:DNA, Ribosomal / Q000737:chemistry*; D008969:Molecular Sequence Data; D010802:Phylogeny; D012341:RNA, Ribosomal, 5S / Q000235:genetics*; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
chemical_list: D004275:DNA, Ribosomal; D012341:RNA, Ribosomal, 5S