title: Evolutionary Dynamics of rDNAs and U2 Small Nuclear DNAs in Triportheus (Characiformes, Triportheidae): High Variability and Particular Syntenic Organization.
abstract: Multigene families correspond to a group of genes tandemly repeated, showing enormous diversity in both number of units and genomic organization. In fishes, unlike rDNAs that have been well explored in cytogenetic studies, U2 small nuclear RNA (snRNA) genes are poorly investigated concerning their chromosomal localization. All Triportheus species (Characiformes, Triportheidae) studied so far carry a ZZ/ZW sex chromosomes system, where the W chromosome contains a huge 18S rDNA cistron. In some species the syntenic organization of rDNAs on autosomes was also verified. To explore this particular organization, we performed three-color-fluorescence in situ hybridization using 5S, 18S rDNA, and U2 snRNA genes as probes in eight Triportheus species. This work represents the first one analyzing the chromosomal distribution of U2 snRNA genes in genomes of Triportheidae. The variability in number of rDNA clusters, and the divergent syntenies for these three multigene families, put in evidence their evolutionary dynamism, revealing a much more complex organization of these genes than previously supposed for closely related species. Our study also provides additional data on the accumulation of repetitive sequences in the sex-specific chromosome. Besides, the chromosomal organization of U2 snDNAs among fish species is also reviewed.
authors.affiliation: 1 Departamento de Genética e Evolução, Universidade Federal de São Carlos , São Carlos, Brazil .
authors.forename: Cassia Fernanda
authors.initials: CF
authors.lastname: Yano
authors.affiliation: 1 Departamento de Genética e Evolução, Universidade Federal de São Carlos , São Carlos, Brazil .
authors.forename: Luiz Antonio Carlos
authors.initials: LA
authors.lastname: Bertollo
authors.affiliation: 2 Laboratorio de Genética, Facultad de Ciencias del Mar y Ambientales, Universidad de Cádiz , Cádiz, Spain .
authors.forename: Laureana
authors.initials: L
authors.lastname: Rebordinos
authors.affiliation: 2 Laboratorio de Genética, Facultad de Ciencias del Mar y Ambientales, Universidad de Cádiz , Cádiz, Spain .
authors.forename: Manuel Alejandro
authors.initials: MA
authors.lastname: Merlo
authors.affiliation: 3 Jena University Hospital, Friedrich Schiller University , Institute of Human Genetics, Jena, Germany .
authors.forename: Thomas
authors.initials: T
authors.lastname: Liehr
authors.affiliation: 2 Laboratorio de Genética, Facultad de Ciencias del Mar y Ambientales, Universidad de Cádiz , Cádiz, Spain .
authors.forename: Silvia
authors.initials: S
authors.lastname: Portela-Bens
authors.affiliation: 1 Departamento de Genética e Evolução, Universidade Federal de São Carlos , São Carlos, Brazil .
authors.forename: Marcelo de Bello
authors.initials: MB
authors.lastname: Cioffi
mesh_terms: D000818:Animals; D060125:Characiformes / Q000235:genetics*; D002874:Chromosome Mapping; D004275:DNA, Ribosomal / Q000235:genetics*; D019143:Evolution, Molecular; D005260:Female; D014644:Genetic Variation; D016678:Genome; D059785:Karyotype; D007621:Karyotyping; D008297:Male; D005810:Multigene Family; D012342:RNA, Small Nuclear / Q000235:genetics*; D013045:Species Specificity; D026801:Synteny / Q000235:genetics*
chemical_list: D004275:DNA, Ribosomal; D012342:RNA, Small Nuclear; C405484:U2 small nuclear RNA
keywords: multigene families; repetitive DNAs; sex chromosomes