Physical Mapping of 5S rDNA in Two Species of Knifefishes: <i>Gymnotus pantanal</i> and <i>Gymnotus paraguensis</i> (Gymnotiformes)

Abstract

Physical mapping of 5S rDNA in 2 species of knifefishes, Gymnotuspantanal and G. paraguensis (Gymnotiformes), was performed using fluorescence in situ hybridization with a 5S rDNA probe. The 5S rDNA PCR product from the genomes of both species was also sequenced and aligned to determine non-transcribed spacer sequences (NTS). Both species under study had different patterns of 5S rDNA gene cluster distribution. While in the karyotype of G. pantanal two 5S rDNA-bearing pairs were observed, the karyotype of G. paraguensis possessed as many as 19 such pairs. Such multiplication of 5S rDNA gene clusters might be caused by the involvement of transposable elements because the NTS of G. paraguensis was 400 bp long with high identity (90%) with a mobile transposable element called Tc1-like transposon, described from the cyprinid fish Labeo rohita.

Comparative Chromosome Mapping of U2 snRNA and 5S rRNA Genes in <b><i>Gymnotus</i></b> Species (Gymnotiformes, Gymnotidae): Evolutionary Dynamics and Sex Chromosome Linkage in <b><i>G</i></b>. <b><i>pantanal</i></b>

“…By means of distinct molecular cytogenetic techniques, Almeida-Toledo et al [2000a, b] and da Silva et al [2011] showed that the origin of multiple sex chromosomes in the 3 Gymnotiformes species involved the fusion between X 1 and X 2 giving rise to the Y in males. However, in E .…”

“…Moreover, the 5S and 18S ribosomal multigene families show a singular situation concerning the chromosomal location in this fish group. Thus, while the distribution of 5S ribosomal DNA (rDNA) is extremely variable when comparing distant or close species (due to the association with transposable elements) [da Silva et al, 2011;Scacchetti et al, 2011], the NOR-bearing chromosome pair is homeologous in several species .The chromosomal location of ribosomal sites has been extensively described in fish during the last few years, while other repetitive sequences have been poorly explored, in- …”

High Evolutionary Dynamism in 5S rDNA of Fish: State of the Art

“…Therefore HT could be the mechanism responsible for a lateral movement of genes between eukaryotes [Merlo et al, 2012a, b]. The 5S rDNA family is an excellent candidate for this kind of HT, since interactions between retrotransposons and 5S rDNA have been demonstrated [Kapitonov and Jurka, 2003;da Silva et al, 2011], and this interaction could open the way for a 5S rRNA gene lateral transfer [Merlo et al, 2012a, b].…”

Evolutionary Dynamics of Repetitive DNA in <b><i>Semaprochilodus </i></b>(Characiformes, Prochilodontidae): A Fish Model for Sex Chromosome Differentiation

“…In Neotropical fishes, all known classes of these elements have been identified, and it is believed that the elements are responsible for numerous chromosomal rearrangements, as observed in the genera Gymnotus [da Silva et al, 2011], Cichla [Valente et al, 2011] and Symphysodon [Gross et al, 2009]. Thus, repetitive DNAs have been widely applied as physical chromosomal markers in comparative studies for locating chromosomal rearrangements, identifying and characterizing sex chromosomes and analyzing chromosomal evolution in Neotropical fishes [Gross et al, 2009;Machado et al, 2011;Schemberger et al, 2011;Terencio et al, 2012a, b;Schneider et al, 2013a, b].…”