Herança, manutenção e origem dos diferentes tipos de cromossomos B em Prochilodus lineatus (Characiformes, Prochilodontidae) do rio Mogi-Guaçu

Prochilodus lineatus is a species of high incidence in the upper Paraná River basin, involving mainly the Grande, Pardo and Mogi-Guaçu Rivers. Cytogenetically, this species has a diploid number of 54 meta/submetacentric chromosomes and presents an interesting system of B microchromosomes, which can occur interindividual variation from zero up to nine supernumeraries, also it presents polymorphism and can be found in different morphotypes. P. lineatus can be considered a model species of neotropical fish, commonly used for studies concerning the origin, behavior and evolution of B chromosomes, due to ease of capture, handling, high frequency of supernumerary and polymorphism. Currently, there are only speculations about its function, origin and inheritance, which make the analysis of the DNA structure of this chromosomal type, as well as the study of the inheritance pattern, of the utmost importance. Faced with this, the present work aimed to study the origin, maintenance and inheritance of the B chromosomes variants found in P. lineatus from Mogi-Guaçu River, from DNA composition analysis, frequency in natural population and transmission pattern of these genomic elements. The results obtained from the inheritance analysis of these supernumerary showed a dynamism between supernumerary variants to prevail in the host genome through the transmission pattern (kB), in which the B-metacentric morphotype presented kB above Mendelian ratio, indicating a possible accumulation mechanism (drive), while the B-acro and B-submetacentric variants presented kB below Mendelian ratio, indicating that they were in extinction stage. When performing the chromosome painting technique, using B-specific probes obtained from each microdissected morphotypes, it was observed a homology between the B chromosome variants, indicating a common ancient variant origin. However, only the B-submetacentric chromosome probe (Bsm) showed ...Prochilodus lineatus constitui-se em uma espécie de grande ocorrência na bacia superior do rio Paraná, envolvendo, sobretudo, os rios Grande, Pardo e Mogi-Guaçu. Citogeneticamente, essa espécie apresenta número diploide de 54 cromossomos dos tipos meta/submetacêntricos e apresenta um interessante sistema de microcromossomos B, que pode ocorrer variação interindividual de zero a nove supranumerários, além de apresentar polimorfismo, sendo encontrados diferentes morfotipos. P. lineatus pode ser considerada uma espécie modelo de peixe neotropical, sendo muito utilizada para estudos concernentes à origem, comportamento meiótico e evolução dos cromossomos B, devido à facilidade de captura, manejo, alta frequência de supranumerários e polimorfismo. Atualmente existem muitas especulações a respeito de sua função, origem e herança, o que torna a análise da estrutura do DNA deste tipo cromossômico, assim como o estudo do seu padrão de herança de extrema importância. Diante disto, o presente trabalho teve como objetivo estudar a origem, manutenção e herança das variantes de cromossomos B encontradas em P. lineatus do rio Mogi-Guaçu, a partir da análise da composição do DNA, frequência na população natural e padrão de transmissão destes elementos genômicos. Os resultados obtidos a partir da análise da herança destes supranumerários mostrou dinamismo entre as variantes de supranumerários para prevalecerem nos genomas hospedeiros, por meio do padrão de transmissão (kB), onde o morfotipo B-metacêntrico apresentou kB acima da taxa Mendeliana, indicando um possível mecanismo de acúmulo (drive), enquanto que os morfotipos B-acro e B-submetacêntrico apresentaram kB abaixo da taxa Mendeliana, indicando estarem em estágio de extinção. Ao realizar a técnica de pintura cromossômica, utilizando as sondas B-específicas obtidas a partir da microdissecção de cada morfotipo, observou-se ..

B chromosomes in the species Prochilodus argenteus (Characiformes, Prochilodontidae): morphologicalidentity and dispersion

Volume: 9Start Page: 79End Page: 8

Karyotypic conservatism in five species of Prochilodus (Characiformes, Prochilodontidae) disclosed by cytogenetic markers

The family Prochilodontidae is considered a group with well conserved chromosomes characterized by their number, morphology and banding patterns. Thence, our study aimed at accomplishing a cytogenetic analysis with conventional methods (Giemsa staining, silver staining of the nucleolus organizer regions-AgNOR, and C-banding) and fluorescence in situ hybridization (FISH) with 18S and 5S ribosomal DNA probes in five species of the Prochilodus genus (Prochilodus argenteus, Prochilodus brevis, Prochilodus costatus, Prochilodus lineatus and Prochilodus nigricans) collected from different Brazilian hydrographic basins. The results revealed conservatism in chromosome number, morphology, AgNORs 18S and 5S rDNAs location and constitutive heterochromatin distribution patterns. The minor differences observed in this work, such as an Ag-NOR on a P. argenteus chromosome and a distinct C-banding pattern in P. lineatus, are not sufficient to question the conservatism described for this group. Future work using repetitive DNA sequences as probes for FISH will be interesting to further test the cytogenetic conservatism in Prochilodus. © 2013, Sociedade Brasileira de Genética.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Transmission rate variation among three B chromosome variants in the fish Prochilodus lineatus (Characiformes, Prochilodontidae)

Estudos citogenéticos foram desenvolvidos em Prochilodus lineatus (Valenciennes 1836), os quais descrevem um interessante sistema de pequenos cromossomos supranumerários. O objetivo deste trabalho foi estudar a frequência e morfologia dos cromossomos B em indivíduos a partir da linhagem parental e os padrões de herança destes elementos em indivíduos obtidos a partir de cruzamentos controlados na espécie P. lineatus. A taxa de transmissão dos cromossomos B revelaram um kB=0,388 para o tipo acrocêntrico, kB=0,507 para o tipo metacêntrico e kB=0,526 submetacêntrico. Os resultados obtidos levantam hipóteses de que os cromossomos B do tipo acrocêntrico se encontram em fase de extinção, enquanto que os supranumerários do tipo metacêntrico e submetacêntrico encontram-se em fase de neutralização, seguindo uma taxa de transmissão Mendeliana.Cytogenetic studies were developed in Prochilodus lineatus (Valenciennes 1836), describing an interesting system of small supernumerary chromosomes. The purpose of this work is to study the frequency and morphology of B chromosomes in individuals from the parental line and the inheritance patterns of these elements in individuals obtained from controlled crosses in the species P. lineatus. The transmission rate of B chromosomes revealed a kB=0.388 for the acrocentric type, a kB=0.507 for the metacentric type and a kB=0.526 for the submetacentric type. The obtained results raise hypothesis that B-acrocentric chromosomes are involved in an extinction process in this species, while the metacentric and submetacentric supernumerary elements comprises a neutral mechanism and follows a Mendelian transmission rate

New Insights into Karyotypic Relationships Among Populations of Astyanax bockmanni (Teleostei, Characiformes) of Different Watersheds

The fish constitute about 50% of all vertebrates, including a wide morphological and biological diversity, where the genus Astyanax is the most common and diverse, as described in virtually all freshwater environments. By occupying a basal position in the phylogeny of vertebrates, fish are an extremely favorable group for cytogenetic and evolutionary studies. The karyotype found in genus Astyanax diversity may involve a number of polymorphisms, which may be related to ploidy and karyotypic macrostructure, presence of B chromosomes, heterochromatin polymorphisms, and location of ribosomal genes. Nevertheless, the relationship between populations of this species is still poorly studied. Thus, the present work aimed to investigate karyotype variation, chromosomal relationships, and the behavior of 5S and 18S ribosomal genes in six populations of Astyanax bockmanni. The results confirmed the diploid number of 50 chromosomes in all the populations sampled, with the occurrence of one supernumerary chromosome in just one of them. In addition, all populations showed divergent patterns of constitutive heterochromatin and repetitive nucleolar sites. The fluorescence in situ hybridization (FISH) technique using 5S and 18S rDNA probes revealed distinct patterns of distribution for these conserved genes, while 5S rDNA genes were found located in two chromosome pairs, the 18S genes showed multiple marks dispersed in the genome characterizing an inter and intraindividual polymorphic behavior, as previously reported to occur with the utilization of the Ag-NOR technique. Thus, besides minor modifications observed in chromosome morphology, the populations of A. bockmanni analyzed revealed a preserved macrostructural feature, especially concerning to the diploid number; on the other hand, differences in microstructural characteristics indicated by the nucleolus organizer region (NOR) location, constitutive heterochromatin patterns, and distribution of ribosomal genes along the genome were clearly evident in the populations from different river basins, even located at short distances.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

B chromosome dynamics in Prochilodus costatus (Teleostei, Characiformes) and comparisons with supernumerary chromosome system in other Prochilodus species

Volume: 11Start Page: 393End Page: 40

The B Chromosomes of Prochilodus lineatus (Teleostei, Characiformes) Are Highly Enriched in Satellite DNAs

B or supernumerary chromosomes are dispensable elements that are widely present in numerous eukaryotes. Due to their non-recombining nature, there is an evident tendency for repetitive DNA accumulation in these elements. Thus, satellite DNA plays an important role in the evolution and diversification of B chromosomes and can provide clues regarding their origin. The characiform Prochilodus lineatus was one of the first discovered fish species bearing B chromosomes, with all populations analyzed so far showing one to nine micro-B chromosomes and exhibiting at least three morphological variants (Ba, Bsm, and Bm). To date, a single satellite DNA is known to be located on the B chromosomes of this species, but no information regarding the differentiation of the proposed B-types is available. Here, we characterized the satellitome of P. lineatus and mapped 35 satellite DNAs against the chromosomes of P. lineatus, of which six were equally located on all B-types and this indicates a similar genomic content. In addition, we describe, for the first time, an entire population without B chromosomes