Mapping of the Retrotransposable Elements <b><i>Rex1</i></b> and <b><i>Rex3</i></b> in Chromosomes of <b><i>Eigenmannia</i></b> (Teleostei, Gymnotiformes, Sternopygidae)

Abstract

Transposable elements constitute a remarkable fraction of the eukaryote genome and show particular capacity to move and insert in specific regions of the genome. This study identified the retrotransposable elements Rex1 and Rex3 in the genomes of 6 cytotypes of Eigenmannia. The sequences were isolated by PCR, sequenced and physically mapped in the chromosomes of these cytotypes, aiming to investigate the organization and distribution of these elements in this fish group, mainly in the sex chromosomes. The FISH physical mapping revealed that both Rex1 and Rex3 elements are dispersed in small clusters throughout the chromosomes of all cytotypes analyzed. However, conspicuous blocks occur in several samples, including an accentuated accumulation of the Rex3 element in X₁ and X₂ chromosomes of Eigenmannia sp. 2 and in the X chromosome of E. virescens. The accumulations are coincident with heterochromatin-rich regions, suggesting that Rex3 played a role in the differentiation process of the sex chromosomes.

Genetic and Chromosomal Differentiation ofRhamdia quelen(Siluriformes, Heptapteridae) Revealed by Repetitive Molecular Markers and DNA Barcoding

“…TEs and TREs have been observed associated with 18S rDNA, in Sorubim lima 39 and Astyanax scabripinnis, 40 and 5S rDNA, in Eigenmannia. 41,42 According to Le Rouzic and Capy, 43 this association may favor the occurence of the recombination of this DNA carrying mutations that may influence not only the genome organization but also the expression of those sequences.…”

Dispersion of transposable elements and multigene families: Microstructural variation in Characidium (Characiformes: Crenuchidae) genomes

“…Rex elements are non-LTR retrotransposons ( Wicker et al , 2007 ) that are extensively distributed through fish genomes ( Ozouf-Costaz et al , 2004 ; Ferreira et al , 2010 ; Borba et al , 2013 ; Schneider et al , 2013 ; Yano et al , 2014 ; Sene et al , 2015 ; Pinheiro et al. , 2016 ), in addition to those of other species.…”

“…Concerning the distribution of Rex1 and Rex3 in the sex chromosomes, no hybridization sites were identified in the Z and W sex chromosomes of Characidium , whereas these elements are involved in sex chromosome evolution in other species. In particular, Rex3 was detected in the Y chromosome of Chionodraco hamatus ( Ozouf-Costaz et al , 2004 ) and X chromosome of Eigenmannia ( Sene et al , 2015 ); Rex1 and Rex3 were found in the W chromosome of Leporinus ( Borba et al. , 2013 ); and Rex1 , Rex3 , and Rex6 were identified in the Z and W chromosomes of Triportheus ( Yano et al , 2014 ).…”

Chromosomal organization of four classes of repetitive DNA sequences in killifish Orestias ascotanensis Parenti, 1984 (Cyprinodontiformes, Cyprinodontidae)

“…However, in the Cyprinodontiform Lebias fasciata (Valenciennes, 1821), FISH mapping has shown that the 28S and 5S ribosomal DNA probes co-localize on a pair of telocentric chromosomes, conserving the 5S locus on the medial position of the chromosome ( Tigano et al 2004 ). In general, these sequences vary among teleosts in relation to the chromosomal distribution due to their association with transposable elements, typically within the internal spacer regions ( Martins and Galetti 2001 , Cabral-de-Mello et al 2011 , Scacchetti et al 2012 , Sene et al 2015 ).…”