Mapeamento físico de genes ribosomais 18S e 5S nos cromossomos de espécies simpáticas do gênero Gymnotus (Teleostei, Gymnotiformes, Gymnotidae)

Foram analisadas citogeneticamente quatro espécies de peixes do gênero Gymnotus, G. sylvius, G. pantherinus, G. inaequilabiatus e G. cf. carapo de componentes de diferentes bacias hidrográficas brasileiras, com o uso de técnicas citogenéticas básicas (coloração com Giemsa, localização das RONs pela marcação com nitrato de Prata e bandamento C) e citomoleculares (coloração com os fluorocromos base-específicos CMA3 e DAPI, hibridação in fluorescente situ (FISH) com sondas de DNAr 18S e 5S, sonda teloméricas (TTAGGG)n e sonda obtida do cromossomo portador das RONs de G. carapo da bacia Amazônica por Fluorescence Activated Cell Sorting (FACS) e caracterização e organização genômica do DNAr 5S). G. sylvius apresentou número diplóide de 40 cromossomos (22m+12sm+6st); G. pantherinus apresentou número diplóide de 52 cromossomos (32m+18sm+2st) e G. inaequilabiatus (42m+10sm+2a) e G. cf. carapo (38m+12sm+4st) apresentaram 54 cromossomos. O bandamento C evidenciou a marcação de pequenos blocos centroméricos em todos os cromossomos de todas as espécies, sendo, porém, detectadas algumas marcações intersticiais em G. sylvius e grandes blocos intersticiais nos cromossomos de G. inaequilabiatus, G. cf. carapo e G. pantherinus. As RONs foram identificadas em apenas um par cromossômico nas quatro espécies e foram coincidentes com a hibridação fluorescente in situ realizada com a sonda para DNAr 18S e a coloração com o fluorocromo CMA3. A hibridação com a sonda para DNAr 5S revelou marcações em até dezessete pares de cromossomos em G. inaequilabiatus e em até quinze pares em G. cf. carapo; dois pares cromossômicos em G. pantherinus e um par em G. sylvius. A hibridação com a sonda para a sequência telomérica (TTAGGG)n revelou marcações nos telômeros de todos os cromossomos dos representantes destas quatro espécies, além de blocos intersticiais no primeiro...Four fish species of the genus Gymnotus comprised by G. sylvius, G. pantherinus, G. inaequilabiatus and G. cf. carapo from different Brazilian hydrographic basins were analyzed using classic cytogenetic (coloration with Giemsa, localization of NORs for silver nitrate marking and C-banding) and molecular cytogenetic techniques with base-specific fluorochrome DAPI and CMA3, fluorescence in situ hybridization (FISH) with probes consisting of 18S and 5S rDNA, telomeric sequences (TTAGGG)n and whole chromosome prepared by Fluorescence Activated Cell Sorting (FACS) of the NOR chromosome, obtained of G. carapo from Amazon basin, as well as a characterization and genomic organization of 5S rDNA. G. sylvius presented a diploid number of 40 chromosomes (22m+12sm+6st); G. pantherinus presented a karyotype with 52 chromosomes (32m+18sm+2st) and G. inaequilabiatus (42m+10sm+2a) and G. cf. carapo (38m+12sm+4st) presented 54 chromosomes. All the species presented the constitutive heterochromatin located in the centromeric region of all chromosomes. Besides that, some interstitial marks were detected in G. sylvius and large interstitial blocks were identified at the chromosomes of G. inaequilabiatus, G. cf. carapo and G. pantherinus. NORs were identified in only one chromosome pair in all species and were coincident with the in situ hybridization using probes of 18S rDNA and the fluorochrome CMA3. FISH using the probes of 5S rDNA revealed marks up to seventeen chromosome pairs in G. inaequilabiatus and up to fifteen pairs in G. cf. carapo, two chromosome pairs in G. pantherinus and one pair in G. sylvius. The telomeric probes were localized at the telomeres of all chromosomes in the four species, as well as interstitial telomeric sequence in the first metacentric pair in G. sylvius and along the NORs in G. inaequilabiatus and G. cf. carapo. The amplification, cloning, sequencing and in situ hybridization... (Complete abstract click electronic access below)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Esttrutura cromossômica e caracterização cariotípica no gênero Characidium (Teleostei, Characiformes, Crenuchidae)

In the present study, eighteen species from the genus Characidium collected at different river basins were analyzed, including C. cf. zebra, C. tenue, C. xavante, C. stigmosum, Characidium sp1, Characidium sp2, Characidium sp3, Characidium sp4, Characidium sp5, Characidium sp6, C. pterostictum, C. vestigipinne, C. rachovii, C. orientale, C. serrano, C. timbuiense, C. vidali e Characidium sp. aff. C. vidali. The analyses involved classical (Giemsa conventional staining and C-banding) and molecular cytogenetic techniques (fluorescent in situ hybridization with ribosomal 5S and 18S, telomeric, microsatellite motifs and U2 snDNA probes, whole chromosome painting using W-specific probe obtained from C. gomesi-CgW). Besides that, DNA sequencing of restriction-associated DNA (RAD) was carried out in males and females of C. gomesi. All species showed diploid chromosome numbers of 2n=50, with karyotypes mainly composed of meta- and submetacentric types, besides the occurrence of supernumerary chromosomes in Characidium sp. aff. C. vidali and one acrocentric pair in C. pterostictum, C. serrano e C. timbuiense. Also, almost all the analyzed species showed a ZZ/ZW sex chromosome system in distinct evolutionary stages, except Characidium cf. zebra, C. tenue, C. xavante e C. stigmosum. The constitutive heterochromatin was located differentially on the W chromosomes and in interstitial and telomeric position on the Z chromosomes, as well as in the B chromosomes of Characidium sp. aff. C. vidali. 5S rDNA was differentially distributed in the different species, with variations on the number of clusters per genome and position in the karyotype, while the 18S rDNA was conserved in number of sites per genome and variable in location. Conversely, the U2 snDNA distribution was conserved in a single homologous chromosome pair in all species, except in Characidium sp. aff. C. vidali and Characidium sp2. Telomeric probes revealed species with several interstitial...No presente estudo, foram analisadas dezoito espécies de peixes do gênero Characidium, C. cf. zebra, C. tenue, C. xavante, C. stigmosum, Characidium sp1, Characidium sp2, Characidium sp3, Characidium sp4, Characidium sp5, Characidium sp6, C. pterostictum, C. vestigipinne, C. rachovii, C. orientale, C. serrano, C. timbuiense, C. vidali e Characidium sp. aff. C. vidali de diferentes bacias hidrográficas brasileiras, com o uso de técnicas citogenéticas básicas (coloração com Giemsa e bandamento C) e moleculares (hibridação in situ fluorescente com sondas de DNAr 18S e 5S, DNA telomérico (TTAGGG)n e 4 sequências de microssatélites ((CA)15, (GA)15, (CG)15 e (TTA)10), e pintura cromossômica através da microdissecção e amplificação do cromossomo sexual W de C. gomesi (sonda chamada de CgW). Além disso, foi realizado o sequenciamento de DNA associado a sítios de restrição pela enzima SbfI (RAD-tags) através do sistema Illumina Genome Analyzer em machos e fêmeas de C. gomesi. Todas as espécies apresentaram número diploide de 2n=50 cromossomos, com predominância dos cromossomos dos tipos meta e submetacêntricos, além da ocorrência de cromossomos supranumerários em Characidium sp. aff. C. vidali e um par cromossômico acrocêntrico exclusivo detectado em C. pterostictum, C. serrano e C. timbuiense. Foi observada também a ocorrência de um sistema ZZ/ZW de cromossomos sexuais em distintos estágios de diferenciação em todas as espécies, com exceção de Characidium cf. zebra, C. tenue, C. xavante e C. stigmosum. A análise da heterocromatina constitutiva por bandamento C revelou a presença de heterocromatina nos cromossomos sexuais, principalmente no cromossomo W e em blocos intersticiais e/ou teloméricos nos braços longos do cromossomo Z e nos cromossomos Bs de Characidium sp. aff. C. vidali. Sequências de DNAr 5S foram localizadas em diferentes cromossomos, com variação na quantidade de sítios entre as espécies,...Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Scattered organization of the histone multigene family and transposable elements in Synbranchus

The fish species Synbranchus marmoratus is widely distributed throughout the Neotropical region and exhibits a significant karyotype differentiation. However, data concerning the organization and location of the repetitive DNA sequences in the genomes of these karyomorphs are still lacking. In this study we made a physical mapping of the H3 and H4 histone multigene family and the transposable elements Rex1 and Rex3 in the genome of three known S. marmoratus karyomorphs. The results indicated that both histone sequences seem to be linked with one another and are scattered all over the chromosomes of the complement, with a little compartmentalization in one acrocentric pair, which is different from observations in other fish groups. Likewise, the transposable elements Rex1 and Rex3 were also dispersed throughout the genome as small clusters. The data also showed that the histone sites are organized in a differentiated manner in the genomes of S. marmoratus, while the transposable elements Rex1 and Rex3 do not seem to be compartmentalized in this group.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Mapping five repetitive DNA classes in sympatric species of Hypostomus (Teleostei: Siluriformes: Loricariidae): analysis of chromosomal variability

Fish belonging to the genus Hypostomus are known for exhibiting a striking diversity in its karyotype structure, however the knowledge concerning the distribution patterns of heterochromatin and location of repetitive DNA sequences in the karyotypes is still limited. Aiming a better understanding of the chromosomal organization in this group, we analyzed three sympatric species of Hypostomus collected in the Hortelã stream, a component of the Paranapanema River basin, Botucatu/SP/Brazil. The analyses involved the cytogenetic characterization and chromosomal mapping of repetitive sequences and intra/interspecific comparisons using sequences of the cytochrome C oxidase subunit I. The results revealed that H. ancistroides presents a karyotype with 2n = 68 chromosomes, H. strigaticeps 2n = 72 chromosomes, and H. nigromaculatus 2n = 76 chromosomes. In addition to differences found in the diploid number, it was also observed variations in karyotypic formulae, amount of constitutive heterochromatin, and location of nucleolus organizer regions. The cytogenetic mapping of 5S and 18S rDNA, as well as of the H3 histone gene, disclosed a differential dispersion process among the three species. In some cases the Rex1 transposable element showed to be co-located with 5S rDNA sites. The molecular analyses support the cytogenetic data and represent an additional tool for the characterization of the analyzed species. The results evidenced that chromosomal variations are not restricted to differences in diploid number or karyotypic macrostructure in the genus Hypostomus, indicating that events such as transposition of heterochromatin and rDNA segments may participate in the differentiation process occurred in these species. © 2013 Springer Science+Business Media Dordrecht

Extensive spreading of interstitial telomeric sites on the chromosomes of Characidium (Teleostei, Characiformes)

Characidium comprises several species of small freshwater fish that display conserved diploid chromosome numbers and karyotypic formulae. In this study, a comparative cytogenetic analysis using telomeric DNA probes was carried out in nine species of Characidium; a molecular phylogenetic analysis with mitochondrial DNA was also performed in order to investigate the direction of the evolutionary chromosome changes observed here. Our results showed the existence of species with several and variable interstitial telomeric sites (ITSs), with other species showing only terminal signals in their chromosomes. Molecular phylogenetic data suggested that these ITSs emerged once in the evolutionary history of Characidium and were later differentially spread in distinct species/populations of this clade. Additionally, the origin of an exclusive acrocentric pair found in C. pterostictum, C. serrano and C. timbuiense was also investigated, revealing that this pair possibly had a common origin to these species. These results evidence the occurrence of intense and continuous genomic changes among species of Characidium.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Repetitive DNA Sequences and Evolution of ZZ/ZW Sex Chromosomes in <i>Characidium</i> (Teleostei: Characiformes)

<div><p><i>Characidium</i> constitutes an interesting model for cytogenetic studies, since a large degree of karyotype variation has been detected in this group, like the presence/absence of sex and supernumerary chromosomes and variable distribution of repetitive sequences in different species/populations. In this study, we performed a comparative cytogenetic analysis in 13 <i>Characidium</i> species collected at different South American river basins in order to investigate the karyotype diversification in this group. Chromosome analyses involved the karyotype characterization, cytogenetic mapping of repetitive DNA sequences and cross-species chromosome painting using a W-specific probe obtained in a previous study from <i>Characidium gomesi</i>. Our results evidenced a conserved diploid chromosome number of 2n = 50, and almost all the species exhibited homeologous ZZ/ZW sex chromosomes in different stages of differentiation, except <i>C</i>. cf. <i>zebra</i>, <i>C</i>. <i>tenue</i>, <i>C</i>. <i>xavante</i> and <i>C</i>. <i>stigmosum</i>. Notably, some ZZ/ZW sex chromosomes showed 5S and/or 18S rDNA clusters, while no U2 snDNA sites could be detected in the sex chromosomes, being restricted to a single chromosome pair in almost all the analyzed species. In addition, the species <i>Characidium</i> sp. aff. <i>C</i>. <i>vidali</i> showed B chromosomes with an inter-individual variation of 1 to 4 supernumerary chromosomes per cell. Notably, these B chromosomes share sequences with the W-specific probe, providing insights about their origin. Results presented here further confirm the extensive karyotype diversity within <i>Characidium</i> in contrast with a conserved diploid chromosome number. Such chromosome differences seem to constitute a significant reproductive barrier, since several sympatric <i>Characidium</i> species had been described during the last few years and no interespecific hybrids were found.</p></div

Metaphase chromosome plates after FISH with CgW probe in different <i>Characidium</i> species.

<p>The sex chromosomes are indicated. Bar = 10 μm.</p

Giemsa, C-banding, FISH with the 18S rDNA probe (red), 5S rDNA (green) and with CgW probe (red) of different Z and W chromosomes of <i>Characidium</i> species.

<p>Bar = 5 μm.</p