Origin of B chromosomes in the genus Astyanax (Characiformes, Characidae) and the limits of chromosome painting
Eukaryote genomes are frequently burdened with the presence of supernumerary (B) chromosomes. Their origin is frequently investigated by chromosome painting, under the hypothesis that sharing the repetitive DNA sequences contained in the painting probes is a sign of common descent. However, the intragenomic mobility of many anonymous DNA sequences contained in these probes (e.g., transposable elements) adds high uncertainty to this conclusion. Here we test the validity of chromosome painting to investigate B chromosome origin by comparing its results for seven B chromosome types in two fish species genus Astyanax, with those obtained (1) by means of the physical mapping of 18S ribosomal DNA (rDNA), H1 histone genes, the As51 satellite DNA and the (AC)15 microsatellite, and (2) by comparing the nucleotide sequence of one of these families (ITS regions from ribosomal DNA) between genomic DNA from B-lacking individuals in both species and the microdissected DNA from two metacentric B chromosomes found in these same species. Intra- and inter-specific painting suggested that all B chromosomes that were assayed shared homologous DNA sequences among them, as well as with a variable number of A chromosomes in each species. This finding would be consistent with a common origin for all seven B chromosomes analyzed. By contrast, the physical mapping of repetitive DNA sequences failed to give support to this hypothesis, as no more than two B-types shared a given repetitive DNA. Finally, sequence analysis of the ITS regions suggested that at least some of the B chromosomes could have had a common origin.
KeywordsB chromosome rDNA Satellite DNA Microsatellites Chromosome painting
Compliance with ethical standards
This research was funded by grant from the Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) to DMZA (2011/16825-3), grants from Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) to FF and by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES). The funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Conflict of interest
All authors declare that they have no competing interests.
Samples were collected in accordance with Brazilian environmental protection legislation (collection permission MMA/IBAMA/SISBIO—number 3245), and the procedures for sampling, maintenance and analysis of the samples were performed in compliance with international guidelines for the care and use of animals followed by the Brazilian College of Animal Experimentation (COBEA) and was approved (protocol 405) by the Bioscience Institute/UNESP Ethics Committee on the Use of Animals (CEUA).
- Eschmeyer WN Catalog of fishes. California Academy of Sciences, electronic version http://www.calacademy.org/scientists/projects/catalog-of-fishes. Accessed date 15 Dec 2015
- Moreira-Filho O, Bertollo LCA (1991) Astyanax scabripinnis (Pisces, Characidae). A species complex. Braz J Genet 14:331–357Google Scholar
- Pansonato-Alves JC, Hilsdorf AWS, Utsunomia R, Silva DMZA, Oliveira C et al (2013) Chromosomal mapping of repetitive DNA and cytochrome C oxidase I sequence analysis reveal differentiation among sympatric samples of Astyanax fasciatus (Characiformes, Characidae). Cytogenet Genome Res 141(2–3):133–142CrossRefPubMedGoogle Scholar
- Pazza R, Kavalco KF, Bertollo LAC (2006) Chromosome polymorphism in Astyanax fasciatus (Teleostei, Characidae). 1. Karyotypic analysis, Ag-NORs and mapping of the 18S and 5S ribosomal genes in sympatric karyotypes and their possible hybrid forms. Cytogenet Genome Res 112:313–319CrossRefPubMedGoogle Scholar
- Silva DMZA, Pansonato-Alves JC, Utsunomia R, Daniel SN, Hashimoto DT et al (2013) Chromosomal organization of repetitive DNA sequences in Astyanax bockmanni (Teleostei, Characiformes): dispersive location, association and co-localization in the genome. Genetica 141:329–336CrossRefPubMedGoogle Scholar