Molecular organization of 5S rDNA in fishes of the genusBrycon

Abstract

There are few reports on the genomic organization of 5S rDNA in fish species. To characterize the 5S rDNA nucleotide sequence and chromosomal localization in the Neotropical fishes of the genus Brycon, 5S rDNA copies from seven species were generated by PCR. The nucleotide sequences of the coding region (5S rRNA gene) and the nontranscribed spacer (NTS) were determined, revealing that the 5S rRNA genes were highly conserved, while the NTSs were widely variable among the species analyzed. Moreover, two classes of NTS were detected in each species, characterized by base substitutions and insertions-deletions. Using fluorescence in situ hybridization (FISH), two 5S rDNA chromosome loci that could be related to the two 5S rDNA NTS classes were observed in at least one of the species studied. 5S rDNA sequencing and chromosomal localization permitted the characterization of Brycon spp. and suggest a higher similarity among some of them. The data obtained indicate that the 5S rDNA can be an useful genetic marker for species identification and evolutionary studies.

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

“…However, NTS II also separated R. lalandii from R. porosus in phylogenetic trees, due to five consistent base substitutions, showing that the NTS II can be useful for phylogenetic inference in shark species. This result is in agreement with those obtained for the neotropical characiform Leporinus (Ferreira et al, 2006) and Brycon (Wasko et al, 2001), in which the NTS effectively separated closely related species, but it contrasts with the results obtained by Pasolini et al (2006) for the equivalent NTS II existing in rays, as well as those by Robles et al (2005) for sturgeons and by Sajdak et al (1998) for Coregonus. In view of these contradictory results, NTS sequences must be used with caution in evolutionary surveys.…”

“…The set of primers 5SA (5k-TAC GCC CGA TCT CGT CCG ATC-3k) and 5SB (5k-CAG GCT GGT ATG GCC GTA AGC-3k), based on the 5S gene sequence of Salmo gardnerii, described by Komiya & Takemura (1979) and applied successfully to other fish species Wasko et al, 2001), was used for PCR. The primers 5SA and 5SB were designed to amplify the entire NTS and 118 bp of the 5S rRNA gene.…”

“…The intense dynamism of 5S rDNA repeats generates variant classes of 5S rDNA, which have been reported in the genomes of several vertebrates, from lampreys to mammals (Komiya et al, 1986 ;Hallenberg et al, 1994;Frederiksen et al, 1997). Particularly in marine and freshwater ray-finned fishes, vast numbers of structural and functional data have demonstrated the occurrence of a dual size-class pattern of organization of the 5S rDNA (Moran et al, 1996 ;Ce´spedes et al, 1999 ;Rocco et al, 1999;Deiana et al, 2000 ;Martins & Galletti, 2001 a ;Wasko et al, 2001 ;Martins et al, 2002 ;Messias et al, 2003 ;Tigano et al, 2004 ;Alves-Costa et al, 2006).…”

Triploid origin of the gibel carp as revealed by 5S rDNA localization and chromosome painting

“…Triploid origin has been suggested referring to its bisexual related species crucian carp (Carassius auratus Linnaeus) with 100 chromosomes, but the karyotypes were generally classified as diploid types because of lack of sufficient genetic evidence (Zhou & Gui 2002). Fluorescence in-situ hybridization (FISH) with labeled 5S rDNA probes is a useful cytogenetic method for chromosome identification (Murakami & Fujitani 1998, Wasko et al 2001, Affonso & Pedro 2005. In fish the 5S rRNA multi-gene family consists of a highly conserved coding sequence of 120 bp forming arrays of hundreds to thousands of tandem copies, which are separated from each other by variable non-transcribed spacers (NTS) (Long & David 1980).…”

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

“…In the rainbow trout (Oncorhynchus mykiss), chromosome hybridization analyses on male and female metaphase spreads revealed a 5S rDNA chromosome sex-specific pattern (Morán et al, 1996). PCR amplified products of 5S rDNA clearly discriminate the Atlantic salmon (Salmo salar), the brown trout (Salmo truta), and their hybrids (Pendás et al, 1995), and also several Neotropical fish species of the genus Brycon (Wasko et al, 2001). PCR was also applied in the identification of the flatfishes Solea solea and Reinhardtius hippoglossoides (Céspedes et al, 1999) and for the identification of smoked fillets of salmon, rainbow trout, and bream (Brama raii) (Carrera et al, 2000).…”