Scattered organization of the histone multigene family and transposable elements in Synbranchus

Abstract

The fish species Synbranchus marmoratus is widely distributed throughout the Neotropical region and exhibits a significant karyotype differentiation. However, data concerning the organization and location of the repetitive DNA sequences in the genomes of these karyomorphs are still lacking. In this study we made a physical mapping of the H3 and H4 histone multigene family and the transposable elements Rex1 and Rex3 in the genome of three known S. marmoratus karyomorphs. The results indicated that both histone sequences seem to be linked with one another and are scattered all over the chromosomes of the complement, with a little compartmentalization in one acrocentric pair, which is different from observations in other fish groups. Likewise, the transposable elements Rex1 and Rex3 were also dispersed throughout the genome as small clusters. The data also showed that the histone sites are organized in a differentiated manner in the genomes of S. marmoratus, while the transposable elements Rex1 and Rex3 do not seem to be compartmentalized in this group.

Organization and Chromosomal Distribution of Histone Genes and Transposable<b><i> Rex</i></b> Elements in the Genome of <b><i>Astyanax bockmanni </i></b>(Teleostei, Characiformes)

“…This hypothesis was already proposed by Hashimoto et al [2011] and was subsequently corroborated and strengthened by Silva et al [2013Silva et al [ , 2014 and Pansonato-Alves et al [2013a]. The idea that these genes could evolve in concert was also reported and discussed for species in other fish groups Pansonato-Alves et al, 2013b;Utsunomia et al, 2014].…”

“…Another intriguing class of repetitive DNA elements is represented by transposable elements, especially those comprising the Rex family. In fish, these sequences are found to be compartmentalized in heterochromatic regions or dispersed throughout the genome [Ferreira et al, 2011b;Utsunomia et al, 2014;Yano et al, 2014;Chalopin et al, 2015]. In Hypostomus nigromaculatus , PansonatoAlves et al [2013b] observed fluorescence signals of transposable elements concentrated as conspicuous blocks on only 3 chromosomes, with small markings dispersed along the remainder of the genome.…”

Cytogenetic Tools to Study the Biodiversity of Neotropical Fish: From the Classic to the Advent of Cell Culture

“…In addition, the technique of FISH showed the U2 snRNA marked in a chromosome linked to sex in the species G. pantanal [102]. In other Neotropical fishes, these two configurations of the location of U2 snRNA gene can be found [83,102,103,113,114].…”

“…In addition, they may be configured by H1 histone or spread throughout the genome [98]. In fishes, there are still a few studies that investigated the location and organization of these sequences, but in some of these studies histones are associated with ribosomal genes [85,98,99], and the genes H1, H3 and H4 are grouped in species of Astyanax [100,101], as well as in the case of Synbranchus, where H3 and H4 are associated and spread throughout the genomes, likely to transposable elements [102]. This conformation was also observed in Orestias ascotanensis [103], where these sequences are organized into small copies.…”

“…In Gymnotus, physical mapping of U2 snRNA sequences showed differences in the distribution of this gene, which can be clustered in homologous chromosomes as in most species or spread in several sites as in G. pantanal, an apomorphic condition [102]. In addition, the technique of FISH showed the U2 snRNA marked in a chromosome linked to sex in the species G. pantanal [102]. In other Neotropical fishes, these two configurations of the location of U2 snRNA gene can be found [83,102,103,113,114].…”