Centric fusions behind the karyotype evolution of neotropical nannostomus pencilfishes (Characiforme, Lebiasinidae): First insights from a molecular cytogenetic perspective

• Autor(a) principal: Sember, Alexandr
• Data de Publicação: 2020
• Outros Autores: Oliveira, Ezequiel Aguiar de, Ráb, Petr, Bertollo, Luiz Antônio Carlos, Freitas, Natália Lourenço de, Viana, Patrik Ferreira, Yano, Cassia Fernanda, Hatanaka, Terumi, Marinho, Manoela Maria Ferreira, Moraes, Renata Luiza Rosa de, Feldberg, Eliana, Cioffi, Marcelo de Bello
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Institucional do INPA
• Texto Completo: https://repositorio.inpa.gov.br/handle/1/15477
• topic: Dna 18s; Dna 5s; Genomic Dna; Acrocentric Chromosome; Animals Experiment; Animals Tissue; Brasil; C Banding; Characiformes; Chromosomal Mapping; Chromosome Number; Chromosome Rearrangement; Comparative Genomic Hybridization; Cytogenetics; Female; In Situ Hybridization, Fluorescence; Gene Cluster; Gene Fusion; Genetic Variability; Genome; Giemsa Stain; Interspecific Hybridization; Karyotype Evolution; Male; Nannostomus; Nannostomus Beckfordi; Nannostomus Eques; Nannostomus Marginatus; Nannostomus Unifasciatus; Neotropics; Nonhuman; Phylogeny; Robertsonian Chromosome Translocation; Whole Genome Sequencing

Lebiasinidae is a Neotropical freshwater family widely distributed throughout South and Central America. Due to their often very small body size, Lebiasinidae species are cytogenetically challenging and hence largely underexplored. However, the available but limited karyotype data already suggested a high interspecific variability in the diploid chromosome number (2n), which is pronounced in the speciose genus Nannostomus, a popular taxon in ornamental fish trade due to its remarkable body coloration. Aiming to more deeply examine the karyotype diversification in Nannostomus, we combined conventional cytogenetics (Giemsa-staining and C-banding) with the chromosomal mapping of tandemly repeated 5S and 18S rDNA clusters and with interspecific comparative genomic hybridization (CGH) to investigate genomes of four representative Nannostomus species: N. beckfordi, N. eques, N. marginatus, and N. unifasciatus. Our data showed a remarkable variability in 2n, ranging from 2n = 22 in N. unifasciatus (karyotype composed exclusively of metacentrics/submetacentrics) to 2n = 44 in N. beckfordi (karyotype composed entirely of acrocentrics). On the other hand, patterns of 18S and 5S rDNA distribution in the analyzed karyotypes remained rather conservative, with only two 18S and two to four 5S rDNA sites. In view of the mostly unchanged number of chromosome arms (FN = 44) in all but one species (N. eques; FN = 36), and with respect to the current phylogenetic hypothesis, we propose Robertsonian translocations to be a significant contributor to the karyotype differentiation in (at least herein studied) Nannostomus species. Interspecific comparative genome hybridization (CGH) using whole genomic DNAs mapped against the chromosome background of N. beckfordi found a moderate divergence in the repetitive DNA content among the species’ genomes. Collectively, our data suggest that the karyotype differentiation in Nannostomus has been largely driven by major structural rearrangements, accompanied by only low to moderate dynamics of repetitive DNA at the sub-chromosomal level. Possible mechanisms and factors behind the elevated tolerance to such a rate of karyotype change in Nannostomus are discussed. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.