Investigação do papel dos DNAs repetitivos na evolução cromossômica de espécies de Apareiodon (Characiformes, Parodontidae)
Traldi, Josiane Baccarin
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Parodontidae comprises the genera Parodon, Apareiodon e Saccodon, including 32 valid species. Of these, 16 occur in Brazil, and only ten defined at species level and one at genus level possess available chromosomal data. Due to the lack of cytogenetic data of Parodontidae species from the Tocantins-Araguaia and Jaguaribe river basins, this study analyzed by cytogenetic (classical and molecular) and molecular (DNA Barcode) methods six populations from the Tocantins-Araguaia river basin (Apareiodon cavalcante, Apareiodon sp.1, Apareiodon sp. 2, Apareiodon machrisi, Apareiodon argenteus and Parodon cf. pongoensis) and one species from the Jaguaribe river basin (Apareiodon davisi), in order to contribute to the knowledge of the genetic diversity of the family and assist in the understanding of chromosome evolution of this fish group. For all of the Apareiodon analyzed species was identified conservation in diploid number, distribution pattern of heterochromatic blocks and dispersion pattern of repetitive fraction WAp. However, karyotype formula, active nucleolar organizer regions, location of ribosomal genes 45S and 5S and distribution of satellite DNA pPh2004 sites shown to be variable among the species. The (GATA)n and telomeric (TTAGGG)n sequences exhibited similar pattern in A. cavalcante, Apareiodon sp.1, Apareiodon sp. 2 and A. machrisi. In this work, we described the first reports of ribosomal genes co-location for Parodontidae, being observed in A. cavalcante, Apareiodon sp.1, Apareiodon sp. 2, A. machrisi and A. davisi, and also the polymorphism involving the two ribosomal sequences of A. davisi. Analysis of histones H1 and H4 localization represent the first study of histone genes in the family and showed that the seven collected species have co-location of these sequences in a chromosome pair, occuring one additional site of H1 in A. davisi, and dispersed sites of this sequence by the chromosomes of the species. Chromosomal analysis and DNA Barcode performed in A. cavalcante, Apareiodon sp.1, Apareiodon sp. 2 and A. machrisi showed recent divergence among these individual groups, suggesting that Apareiodon sp. 2 is a possible new species, and Apareiodon sp. 1 is a population of A. machrisi. This work contributed to the knowledge of the genetic diversity of viii Parodontidae, presenting unpublished chromosomal and molecular data of this family. General analysis of chromosomal data of this family revealed conservation of karyotype macrostructure, however, more detailed analyzes indicated the occurrence of a great variety of chromosomal microstructural level. The results presented in this study, along with that available in literature, indicated that this microstructure chromosome diversity is clearly linked to repetitive DNAs dynamics.