Evidence of the differentiated structural arrangement of constitutive heterochromatin between two populations of Astyanax scabripinnis (Pisces, Characidae)

Abstract

The composition of heterochromatin classes along the chromosomes of specimens from two populations of the fish Astyanax scabripinnis was examined using fluorescence banding with GC-and AT-DNA specific fluorochromes and fluorescence in situ hybridization (FISH) with an AT-rich satellite DNA (As51) probe. For the pericentromeric heterochromatin blocks neither GC/AT-DNA specific fluorochromes nor the FISH technique produce any response with chromosomes from either of the populations. On the other hand, the telomeric distal heterochromatin blocks of both populations fluoresced when the FISH technique was applied but showed distinct responses after GC-specific fluorochrome treatments, leading us to propose different structural arrangements of the FISH-positive heterochromatins. Such differences in chromosome banding patterns together with other karyotypic differences suggest differentiation of these populations at taxonomic level.

Satellite DNA sites in four species of the genus Astyanax (Teleostei, Characiformes)

“…The two other species possibly occupy a more derived position. Furthermore, A. scabripinnis showed different number of clusters and distribution patterns of such satellite DNA Mantovani et al, 2004), as did Astyanax fasciatus (Pazza et al, 2006). The distribution of 5S rDNA sites in Astyanax also pointed to the occurrence of two main groups, which is in agreement with the data herein reported.…”

“…Its GCpositive heterochromatin distribution was similar to the one reported for other populations from the Tietê river basin (Souza et al, 1996). The exceptions were the single chromosome with a fluorescence signal, an exclusive trait of the population herein analyzed (Figure 2-a), and the distribution of the As-51 satellite DNA (Figure 3-a), less abundant than in the populations from the upper Paraná river basin (Mantovani et al, 2004;Abel et al, 2006). 532 Kavalco et al In A. parahybae, the heterochromatin was distributed in the pericentromeric regions of almost all chromosomes and in the terminal regions of a few ones (Figure 1-b).…”

Physical mapping of the 18S and 5S ribosomal genes in nine Characidae species (Teleostei, Characiformes)

“…Thus, the localization and/or position of 5S rDNA sites in the Characidae are as variable as the 18S rDNA sites. The presence of two pericentromeric 5S rDNA loci in a medium-sized metacentric pair was also suggested as a putative conserved character in Astyanax (Almeida-Toledo et al, 2002;Mantovani et al, 2004). In fact, this characteristic was shared by the three species of this genus here studied.…”

Heterochromatin diversity and its co-localization with 5S and 45S rDNA sites in chromosomes of four Maxillaria species (Orchidaceae)

“…For example, in the fish species Astyanax scabripinnis terminal C-bands that hybridized with an AT-rich satellite DNA sequence stained positively with mithramycin A in one population and negatively in another population (Mantovani et al, 2004) and it has also been reported that in several Citrus species some 45S rDNA sites are CMA + while others are CMA 0 (Carvalho et al, 2005). Furthermore, the rDNA may apparently exist in distinct chromatin conformations determined by specific epigenetic codes, such as cytosine methylation and post-translational changes in histones (Neves et al, 2005), that could affect its reactivity with fluorochromes.…”