Microsatellite Organization in the B Chromosome and A Chromosome Complement in <b><i>Astyanax</i></b> (Characiformes, Characidae) Species

Abstract

The organization of microsatellites in B and sex chromosomes has been linked to chromosomal evolution in a number of animal groups. Here, the chromosomal organizations of (CA)₁₅, (GA)₁₅, (CG)₁₅, (GACA)₄, and (GATA)₈ microsatellites were examined in several Astyanax species with different diploid numbers: Astyanax mexicanus (2n = 50 + 1 B chromosome), A. altiparanae (2n = 50), A. marionae (2n = 48), A. fasciatus (2n = 46), and A. schubarti (2n = 36). The (CA)₁₅ and (GA)₁₅ microsatellites were dispersed across the chromosomes of A. altiparanae and A. fasciatus but were also observed as clusters (CA and GA for A. altiparanae, and CA for A. fasciatus). In A. marionae and A. schubarti, the (CA)₁₅ and (GA)₁₅ microsatellites were dispersed but were also observed as clustered signals and coincident with heterochromatic regions. In all 4 of these species, the (CG)₁₅ and (GACA)₄ microsatellites were dispersed across chromosomes, and the (GATA)₈ microsatellite was co-localized with 5S rDNA. In A. mexicanus, the (CA)₁₅, (GA)₁₅, (CG)₁₅, (GATA)₈, and (GACA)₄ microsatellites were weakly detected and dispersed across the chromosomes of the A complement. On the B chromosome, signals for the different microsatellites were weak, strong, absent, weak, and absent, respectively. The distribution of microsatellites and the locational relationship between microsatellites and 5S rDNA are discussed, and a possible evolutionary pathway is proposed for microsatellites in Astyanax.

High-throughput analysis unveils a highly shared satellite DNA library among three species of fish genus Astyanax

“…Several repetitive DNAs have been physically mapped in Astyanax , including ribosomal DNA, U snRNA genes, histone genes, transposable elements and microsatellites 24 – 26 . However, only one satDNA has been described in this genus, namely the As51 satDNA found in A. scabripinnis by digestion with the Kpn I restriction enzyme 15 .…”

Chromosomes of Asian cyprinid fishes: cytogenetic analysis of two representatives of small paleotetraploid tribe Probarbini

“…While the bearing of the observed patterns to the dynamics of polyploidy remains unclear, some authors [104, 107] suggested that the preferential targeting of (CA) 15 and (GA) 15 and other microsatellite motifs to telomeric and subtelomeric regions might be functionally linked with the structural formation of telomeres. As microsatellites can be found to be embedded within rDNA clusters [108] and all rDNA sites turned out to be terminal in both species under study, we suppose that (CA) 15 and (GA) 15 dinucleotides might have contributed to the dynamic behavior of rDNA sites in these Probarbini representatives.…”

Genomic Organization and Physical Mapping of Tandemly Arranged Repetitive DNAs in Sterlet<b> </b>(<b><i>Acipenser ruthenus</i></b>)

“…There are many examples where ribosomal genes shared chromosomes with blocks of satellites [Vicari et al, 2010;Barbosa et al, 2015], microsatellites, and retrotransposons [Yano et al, 2014b;Piscor and Parise-Maltempi, 2016] or transposons [Ferreira et al, 2011]. Sometimes, large amounts of the repetitive DNAs might promote rDNA silencing [Vicari et al, 2008], although this is not shown in all cases [Costa et al, 2013].…”

“…Satellite DNA with a similar structure was extensively investigated in the bony fish genus Hoplias [Vicari et al, 2010]. Recently, colocalization of 5S rDNA with the transposon Rex3 in 27 sites, including 26 autosomes and the Y chromosome of Erythrinus erythrinus [Yano et al, 2014a], with the microsatellite (GATA) 8 in Astyanax species [Piscor and Parise-Maltempi, 2016], and with a multigene family represented by the U2 snRNA in Characidium species [Scacchetti et al, 2015] was revealed. In all these cases, the colocalization was species-specific.…”