Comparative Chromosomal Mapping of Microsatellites in &lt;b&gt;&lt;i&gt;Leporinus&lt;/i&gt;&lt;/b&gt; Species (Characiformes, Anostomidae): Unequal Accumulation on the W Chromosomes

Sites and amounts of 5-methylcytosine (5-MeC)-rich chromosome regions were detected in the karyotypes of 9 Brazilian species of Characiformes fishes by indirect immunofluorescence using a monoclonal anti-5-MeC antibody. These species, belonging to the genera Leporinus, Triportheus and Hoplias, are characterized by highly differentiated and heteromorphic ZW and XY sex chromosomes. In all species, the hypermethylated regions are confined to constitutive heterochromatin. The number and chromosome locations of hypermethylated heterochromatic regions in the karyotypes are constant and species-specific. Generally, heterochromatic regions that are darkly stained by the C-banding technique are distinctly hypermethylated, but several of the brightly fluorescing hypermethylated regions merely exhibit moderate or faint C-banding. The ZW and XY sex chromosomes of all 9 analyzed species also show species-specific heterochromatin hypermethylation patterns. The analysis of 5-MeC-rich chromosome regions contributes valuable data for comparative cytogenetics of closely related species and highlights the dynamic process of differentiation operating in the repetitive DNA fraction of sex chromosomes.

Section: Karyotypessupporting

confidence: 88%

“…The largest accumulation of these repeats was found in the long arms of the sex chromosomes which are notably heterochromatic [Cioffi et al, , 2011Poltronieri et al, 2014;Yano et al, 2014]. The accumulation of repetitive DNA sequences in the sex chromosomes of these fishes is highly variable, even among closely related species.…”

Section: Discussionmentioning

confidence: 99%

Hypermethylated Chromosome Regions in Nine Fish Species with Heteromorphic Sex Chromosomes

Schmid

Steinlein

Yano

et al. 2015

“…In fact, it has been postulated that microsatellite accumulation in eukaryotic genomes is nonrandom and that each group of organisms/species show preferential accumulation of specific SSR motifs with a particular chromosomal distribution [Tóth et al, 2000;Ruiz-Ruano et al, 2015]. The (CA) 15 , (GA) 15 and (CG) 15 SSRs were previously mapped in different characiform fishes and had similar subtelomeric distributions in Hoplias , Leporinus and Triportheus species, while 2 Semaprochilodus species showed few centromeric/subtelomeric signals [Cioffi et al, 2011[Cioffi et al, , 2012Poltronieri et al, 2013;Terencio et al, 2013;Yano et al, 2014].…”

Section: Discussionmentioning

confidence: 99%

Chromosomal Mapping of Repetitive DNAs in Characidium (Teleostei, Characiformes): Genomic Organization and Diversification of ZW Sex Chromosomes

Scacchetti

Utsunomia

Pansonato-Alves

et al. 2015

The speciose neotropical genus Characidium has proven to be a good model for cytogenetic exploration. Representatives of this genus often have a conserved diploid chromosome number; some species exhibit a highly differentiated ZZ/ZW sex chromosome system, while others do not show any sex-related chromosome heteromorphism. In this study, chromosome painting using a W-specific probe and comparative chromosome mapping of repetitive sequences, including ribosomal clusters and 4 microsatellite motifs - (CA)₁₅, (GA)₁₅, (CG)₁₅, and (TTA)₁₀ -, were performed in 6 Characidium species, 5 of which possessed a heteromorphic ZW sex chromosome system. The W-specific probe showed hybridization signals on the W chromosome of all analyzed species, indicating homology among the W chromosomes. Remarkably, a single major rDNA-bearing chromosome pair was found in all species. The 18S rDNA localized to the sex chromosomes in C. lanei, C. timbuiense and C. pterostictum, while the major rDNA localized to one autosome pair in C. vidali and C. gomesi. In contrast, the number of 5S rDNA-bearing chromosomes varied. Notably, minor ribosomal clusters were identified in the W chromosome of C. vidali. Microsatellites were widely distributed across almost all chromosomes of the karyotypes, with a greater accumulation in the subtelomeric regions. However, clear differences in the abundance of each motif were detected in each species. In addition, the Z and W chromosomes showed the differential accumulation of distinct motifs. Our results revealed variability in the distribution of repetitive DNA sequences and their possible association with sex chromosome diversification in Characidium species.

“…Recent surveys on chromosomal microsatellite locations showed that organization in sex chromosomes differed between Leporinus and Characidium species [Poltronieri et al, 2014;Scacchetti et al, 2015]. For example, in W chromosomes of the Leporinus species, microsatellites accumulated primarily in heterochromatic regions of the long arms.…”

mentioning

confidence: 99%

“…However, microsatellite distributions differed between the 4 Leporinus species, despite the 4 species exhibiting similar patterns of heterochromatin distribution. This suggested that the heterochromatinization process is dynamic, free of selection, and subject to distinctive mechanisms after speciation [Poltronieri et al, 2014].…”

mentioning

confidence: 99%

Microsatellite Organization in the B Chromosome and A Chromosome Complement in Astyanax (Characiformes, Characidae) Species

Piscor

Parise-Maltempi²

2016

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.