Chromosomal Mapping of Repetitive DNA Sequences in Five Species of <b><i>Astyanax</i></b> (Characiformes, Characidae) Reveals Independent Location of U1 and U2 snRNA Sites and Association of U1 snRNA and 5S rDNA

Abstract

Astyanax is a genus of Characidae fishes currently composed of 155 valid species. Previous cytogenetic studies revealed high chromosomal diversification among them, and several studies have been performed using traditional cytogenetic techniques to investigate karyotypes and chromosomal locations of 18S and 5S rDNA genes. However, only a few studies are currently available about other repetitive sequences. Here, the chromosomal location of small nuclear RNA genes, identified as U1 and U2 snRNA clusters, was established and compared to the distribution of 5S rDNA and histone clusters in 5 Astyanax species (A. paranae, A. fasciatus, A. bockmanni, A. altiparanae, and A. jordani) using FISH. The cytogenetic mapping of U1 and U2 snRNA demonstrated a conserved pattern in the number of sites per genome independent of the location in Astyanax species. The location of the U1 snRNA gene was frequently associated with 5S rDNA sequences, indicating a possible interaction between the distinct repetitive DNA families. Finally, comparisons involving the location of U1 and U2 snRNA clusters in the chromosomes of Astyanax species revealed a very diverse pattern, suggesting that many rearrangements have occurred during the diversification process of this group.

Conserved number of U2 snDNA sites in Piabina argentea, Piabarchus stramineus and two Bryconamericus species (Characidae, Stevardiinae)

“…(Cambuta River) that showed one pair bearing U2 snDNA clusters in interstitial position on the short arm. These observations make it clear that, regardless of chromosomal positions, the number of U2 snDNA sites is conserved for Bryconamericus genus, as well as described for Astyanax genus (Silva et al, 2015;. However, in Astyanax genus almost all species showed two pairs bearing U2 snDNA sites.…”

“…According to Yano et al (2017), in four Triportheus Cope, 1872 species, the U2 snRNA genes are syntenic with both rDNAs (18S and 5S), while in Triportheus albus Cope, 1872, the U2 snRNA genes are syntenic with 18S rDNA and in other three Triportheus species, the U2 snRNA genes are not syntenic with rDNAs. The last described pattern is common in fish (Pelliccia et al, 2001;Manchado et al, 2006;Úbeda-Manzanaro et al, 2010;Utsunomia et al, 2014;Scacchetti et al, 2015;Silva et al, 2015). The aim of the present study was to analyze the chromosomal location of two multigene families (5S rDNA and U2 snDNA) in the genome of Piabina argentea Reinhardt, 1867, Piabarchus stramineus (Eigenmann, 1908) and two Bryconamericus species, in order to obtain a better knowledge about the relationship among U2 snRNA and 5S rRNA genes of species of the subfamily Stevardiinae.…”

“…jordani (Hubbs & Innes, 1936) (Silva et al, 2015) signals in one chromosome pair were detected. On the other hand, eleven Astyanax Baird & Girard, 1854 species showed two chromosomes pairs bearing U2 snDNA clusters (Silva et al, 2015;. The authors showed that, in comparison to other repetitive sequences studied in chromosomes of Bryconamericus and Astyanax, the U2 snDNA is the most conserved.…”

“…(Santos et al, 2017), Astyanax mexicanus (De Filippi, 1853) and A. jordani (Hubbs & Innes, 1936) (Silva et al, 2015) signals in one chromosome pair were detected. On the other hand, eleven Astyanax Baird & Girard, 1854 species showed two chromosomes pairs bearing U2 snDNA clusters (Silva et al, 2015;.…”

Chromosomal evolutionary dynamics of four multigene families in Coreidae and Pentatomidae (Heteroptera) true bugs

“…Stability for number of sites was also observed in the fish genus Astyanax (Characiformes, Characidae) (Silva et al 2015), in contrast with the variability in the number of sites observed in some species of fish of the family Batrachoididae (Úbeda-Manzanaro et al 2010) and grasshoppers belonging to the subfamily Melanoplinae (Palacios- . Another feature of the U2 snRNA sites in heteropterans was the location restricted to autosomes, a feature that is also recurrent in different species of fish (Úbeda-Manzanaro et al 2010;Utsunomia et al 2014), except for Gymnotus pantanal, with U2 snDNA clusters in the sex chromosomes (Utsunomia et al 2014).…”