Dynamics of 5S rDNA in the tilapia (Oreochromis niloticus) genome: repeat units, inverted sequences, pseudogenes and chromosome loci

In higher eukaryotes, the 5S ribosomal DNA (5S rDNA) is organized in tandem arrays with repeat units composed of a coding region and a non-transcribed spacer sequence (NTS). These tandem arrays can be found on either one or more chromosome pairs. 5S rDNA copies from the tilapia fish. Oreochromis niloticus, were cloned and the nucleotide sequences of the coding region and of the non-transcribed spacer were deter-mined. Moreover, the genomic organization of the 5S rDNA tandem repeats was investigated by fluorescence in situ hybridization (FISH) and Southern blot hybridization. Two 5S rDNA classes, one consisting of 1.4-kb repeats and another one with 0.5-kb repeats were identified and designated 5S rDNA type I and type II, respectively, An inverted 5S rRNA gene and a 5S rRNA putative pseudogene were also identified inside the tandem repeats of 5S rDNA type I. FISH permitted the visualization of the 5S rRNA genes at three chromosome loci, one of them consisting of arrays of the 5S rDNA type I, and the two others corresponding to arrays of the 5S rDNA type II. The two classes of the 5S rDNA. The presence of pseudogenes, and the inverted genes observed in the O. niloticus genome might be a consequence of the intense dynamics of the evolution of these tandem repeat elements. Copyright (C) 2002 S. Karger AG, Basel.

Genomic organization and evolution of the 5S ribosomal DNA in Tilapiini fishes

5S rDNA sequences present an intense dynamism and have proved to be valuable as genetic markers to distinguish closed related species and also in the understanding of the evolutionary dynamic of repetitive sequences in the genomes. In order to identify patterns of 5S rDNA organization and their evolution in the genome of fish species, such genomic segment was investigated in the tilapias Oreochromis niloticus and Tilapia rendalli, and in the hybrid O. urolepis hornorum x O. mossambicus. A dual 5S rDNA system was identified in the three analyzed tilapia samples. Although each 5S rDNA class was conserved among the three samples, a distinct 5S rDNA genome organization pattern could be evidenced for each sample. The presence of a dual 5S rDNA system seems to be a general trait among non-related teleost fish orders, suggesting that evolutionary events of duplication have occurred before the divergence of the main groups of teleost fishes.

5S rDNA variation and its phylogenetic inference in the genus Leporinus (Characiformes : Anostomidae)

5S rDNA sequences have proven to be valuable as genetic markers to distinguish closely related species and also in the understanding of the dynamic of repetitive sequences in the genomes. In the aim to contribute to the knowledge of the evolutionary history of Leporinus (Anostomidae) and also to contribute to the understanding of the 5S rDNA sequences organization in the fish genome, analyses of 5S rDNA sequences were conducted in seven species of this genus. The 5S rRNA gene sequence was highly conserved among Leporinus species, whereas NTS exhibit high levels of variations related to insertions, deletions, microrepeats, and base substitutions. The phylogenetic analysis of the 5S rDNA sequences clustered the species into two clades that are in agreement with cytogenetic and morphological data.

Conservation of the 5S-bearing chromosome pair and co-localization with major rDNA clusters in five species of Astyanax (Pisces, Characidae)

Major and 5S ribosomal genes have been localized in chromosomes from five fish species, genus Aslyanax, using in situ hybridization (FISH) with 28S and 5S rDNA probes. In situ signals for the major rDNA co-localized with the 5S rDNA clusters in the pericentromeric region of one marker chromosome in all five species analyzed. The conserved localization of these two rDNA clusters in the five related Astyanax species was considered as indicative of a close relationship among them. The use of these molecular markers for elucidating evolutionary relationships among closely related taxa is discussed. Copyright (C) 2002 S. Karger AG, Basel.

Discrimination of Shark species by simple PCR of 5S rDNA repeats

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

5S rDNA chromosomal mapping and COI sequence analysis reveal differentiation among distinct populations of a characid fish Serrapinnus notomelas

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Genetic identification of the sharks Rhizoprionodon porosus and R. lalandii by PCR-RFLP and nucleotide sequence analyses of 5S rDNA

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Chromosome Mapping of H1 Histone and 5S rRNA Gene Clusters in Three Species of Astyanax (Teleostei, Characiformes)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Molecular Characterization and Physical Mapping of Two Classes of 5S rDNA in the Genomes of Gymnotus sylvius and G. inaequilabiatus (Gymnotiformes, Gymnotidae)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Cytogenetic Mapping of 5S and 18S rRNAs and H3 Histone Genes in 4 Ancient Proscopiidae Grasshopper Species: Contribution to Understanding the Evolutionary Dynamics of Multigene Families

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

The 5S rDNA family evolves through concerted and birth-and-death evolution in fish genomes: an example from freshwater stingrays

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Molecular organization of 5S rDNA in sharks of the genus Rhizoprionodon: insights into the evolutionary dynamics of 5S rDNA in vertebrate genomes

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Chromosomal mapping of repetitive DNAs in the beetle Dichotomius geminatus provides the first evidence for an association of 5S rRNA and histone H3 genes in insects, and repetitive DNA similarity between the B chromosome and A complement

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)