Nucleotide sequence, genomic organization and chromosome localization of 5S rDNA in two species of Curimatidae (Teleostei, Characiformes)

Abstract

The 5S ribosomal DNA (5S rDNA) of higher eukaryotes is organized in repeat units of tandem arrays composed of a 5S rDNA coding region, conserved even among non-related taxa, and a variable non-transcribed spacer sequence (NTS). To contribute to knowledge on the organization and evolution of vertebrate 5S rDNA we used PCR, nucleotide sequencing, Southern blot hybridization and chromosome fluorescence in situ hybridization (FISH) to investigate 5S rDNA tandem repeats in the South American Curimatidae fish Steindachnerina insculpta and Cyphocharax modesta. 5S rDNA repeats of 180 base pairs (bp) from both species were PCR-generated and sequenced evidencing the shortest 5S rDNA monomer so far described in eukaryote species. Southern blotting revealed that both species contained two tandem 5S rDNA classes, the PCR amplified fragment composed of 180 bp monomers and a class of 1600 bp monomers not detected by PCR. Chromosome mapping of the 5S rDNA repeats identified a major locus in both species and a second minor locus only in C. modesta. The Southern blot and chromosome mapping data indicate the presence of different types of 5S rDNA tandem repeats in the Curimatidae genome.

Chromosomal localization of 18S and 5S rDNA using FISH in the genus Tor (Pisces, Cyprinidae)

“…Martins and Wasko (2004) suggested that the 5S rDNA clusters in fishes are most commonly located at interstitial chromosome site and this interstitial position is optimal for its organization in fishes, since it has been found in most species of several orders. Our findings in Tor species are in clear agreement with several studies in fishes that suggested common conservation pattern of 5S rDNA number and location found between closely related fish species (Martins and Galetti 2000;Gromicho et al 2006;Santos et al 2006). Even in the genus Astyanax (Characidae), which is reported for high rates of chromosome variations, 5S rDNA chromosome clusters are conserved among species (AlmeidaToledo et al 2002;Mantovani et al 2005).…”

“…Comparison of the NTS region among selected fishes and four Tor species demonstrated the presence of 81 bp long NTS. Research work on several organisms has shown that the smallest length of NTS sequence of 5S rDNA so far described in eukaryotes, including fishes, is 62 bp (Martins and Wasko 2004;Santos et al 2006).…”

A refined Panax ginseng karyotype based on an ultra-high copy 167-bp tandem repeat and ribosomal DNAs

“…Our previous experiment used 5S rDNA from Brassica rapa [24] , [36] rather than that of B. oleracea as probe. However, coding regions of 5S rDNA are conserved across unrelated taxa [37] , [38] , suggesting that the difference in the ability to detect these loci is likely not related to the probes used but rather to the techniques used for labeling and FISH, which considerably influence the end signal [34] . A karyotypic idiogram of the P. ginseng chromosomes showing the DAPI bands, rDNA and Pg167TR signals is shown in Fig.…”

Chromosome mapping of 18S rDNA and 5S rDNA by dual-color fluorescence in situ hybridization in the half-smooth tongue sole (Cynoglossus semilaevis)

“…Martins and Galetti (1999) regard this as an ancient phenomenon in fishes. In the family Curimatidae, Steindachnerina insculpta has 1 pair of 5S rDNA sites and Cyphocharax modesta has 2 pairs (Santos et al, 2006). In the order Tetraodontiformes, Sphoeroides greeleyi and S. spinosus possess 1 pair of 5S rDNA sites, while Cyclichthys spinosus possesses 2 pairs (Noleto et al, 2007).…”