Composition and Nature of Heterochromatin in the Electrical Fish (Knifefishes) Gymnotus (Gymnotiformes: Gymnotidae)

Fishes of the genus Gymnotus have been suggested as a good model for biogeographic studies in the South American continent. In relation to heterochromatin, species of this genus have blocks preferably distributed in the centromeric region. The content of these regions has been shown to be variable, with description of transposable elements, pseudogenes of 5S rDNA and satellite sequences. In G. carapo Clade, although geographically separated, species with 2n = 54 chromosomes share the distribution of many 5S rDNA sites, a unique case within the genus. Here, repetitive DNA sequences from G. sylvius (2n = 40) and G. paraguensis (2n = 54) were isolated and mapped to understand their constitution. The chromosome mapping by FISH showed an exclusive association in the centromeres of all chromosomes. However, the cross-FISH did not show positive signs of interspecific hybridization, indicating high levels of heterochromatic sequence specificity. In addition, COI-1 sequences were analyzed in some species of Gymnotus, which revealed a close relationship between species of clade 2n = 54, which have multiple 5S rDNA sites. Possibly, the insertion of retroelements or pseudogenization and dispersion of this sequence occurred before the geographic dispersion of the ancestor of this clade from the Amazon region to the hydrographic systems of Paraná-Paraguay, a synapomorphy for the group.

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Chromosomal Mapping of Repetitive DNAs in Characidium (Teleostei, Characiformes): Genomic Organization and Diversification of ZW Sex Chromosomes

Cytogenetic and Genome Research ◽

10.1159/000437165 ◽

2015 ◽

Vol 146 (2) ◽

pp. 136-143 ◽

Cited By ~ 10

Author(s):

Priscilla C. Scacchetti ◽

Ricardo Utsunomia ◽

José C. Pansonato-Alves ◽

Marcelo R. Vicari ◽

Roberto F. Artoni ◽

...

Keyword(s):

Sex Chromosomes ◽

Dna Sequences ◽

Sex Chromosome ◽

Repetitive Sequences ◽

5S Rdna ◽

Chromosome Mapping ◽

Chromosomal Mapping ◽

Specific Probe ◽

W Chromosome ◽

Sex Chromosome System

The speciose neotropical genus Characidium has proven to be a good model for cytogenetic exploration. Representatives of this genus often have a conserved diploid chromosome number; some species exhibit a highly differentiated ZZ/ZW sex chromosome system, while others do not show any sex-related chromosome heteromorphism. In this study, chromosome painting using a W-specific probe and comparative chromosome mapping of repetitive sequences, including ribosomal clusters and 4 microsatellite motifs - (CA)15, (GA)15, (CG)15, and (TTA)10 -, were performed in 6 Characidium species, 5 of which possessed a heteromorphic ZW sex chromosome system. The W-specific probe showed hybridization signals on the W chromosome of all analyzed species, indicating homology among the W chromosomes. Remarkably, a single major rDNA-bearing chromosome pair was found in all species. The 18S rDNA localized to the sex chromosomes in C. lanei, C. timbuiense and C. pterostictum, while the major rDNA localized to one autosome pair in C. vidali and C. gomesi. In contrast, the number of 5S rDNA-bearing chromosomes varied. Notably, minor ribosomal clusters were identified in the W chromosome of C. vidali. Microsatellites were widely distributed across almost all chromosomes of the karyotypes, with a greater accumulation in the subtelomeric regions. However, clear differences in the abundance of each motif were detected in each species. In addition, the Z and W chromosomes showed the differential accumulation of distinct motifs. Our results revealed variability in the distribution of repetitive DNA sequences and their possible association with sex chromosome diversification in Characidium species.

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Advances in the cytogenetics of Annonaceae, the case of Annona cherimola L.

Genome ◽

10.1139/gen-2019-0172 ◽

2020 ◽

Vol 63 (7) ◽

pp. 357-364

Author(s):

Egizia Falistocco ◽

Nicoletta Ferradini

Keyword(s):

Dna Sequences ◽

5S Rdna ◽

Principal Component ◽

Centromeric Heterochromatin ◽

Fluorochrome Banding ◽

Important Species ◽

Annona Cherimola ◽

Rdna Sites ◽

Basic Reference ◽

Dapi Banding

Annonaceae represent the largest extant family among the early divergent angiosperms. Despite the long-standing interest in its evolutionary and taxonomic aspects, cytogenetic studies on this family remain extremely few even on economically important species. With this study, we realized a detailed characterization of the chromosomes of Annona cherimola (2n = 14) by a combination of in situ hybridization techniques, fluorochrome banding, and karyomorphological analysis. FISH revealed that 45S and 5S rDNA sites are co-localized in correspondence to the secondary constrictions of the SAT-chromosome pair. Some hypotheses on the organization of the linked 45S and 5S rDNA repeats have been made. FISH with Arabidopsis-type telomeric arrays demonstrated that the A. cherimola telomeres are constituted by TTTAGGG sequences and that they are exclusively localized at the extremities of chromosomes. An insight into the chromosome structure of A. cherimola was obtained by the self-GISH procedure which revealed highly repeated DNA sequences localized in the centromeric regions of all chromosomes. The correspondence of s-GISH signals with DAPI banding suggests that these sequences are the principal component of the centromeric heterochromatin of this species. The karyotype of A. cherimola here described is proposed as the basic reference karyotype for successive investigations in Annonaceae.

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Extensive Chromosomal Reorganization in Apistogramma Fishes (Cichlidae, Cichlinae) Fits the Complex Evolutionary Diversification of the Genus

International Journal of Molecular Sciences ◽

10.3390/ijms20174077 ◽

2019 ◽

Vol 20 (17) ◽

pp. 4077 ◽

Cited By ~ 2

Author(s):

Gideão Wagner Werneck Félix da Costa ◽

Marcelo de Bello Cioffi ◽

Thomas Liehr ◽

Eliana Feldberg ◽

Luiz Antonio Carlos Bertollo ◽

...

Keyword(s):

Dna Sequences ◽

Tandem Repeats ◽

5S Rdna ◽

Unknown Origin ◽

South American ◽

Biogeographic Patterns ◽

Evolutionary Diversification ◽

Species Complexes ◽

Chromosomal Changes

Neotropical cichlid fishes are one of the most diversified and evolutionarily successful species assemblages. Extremely similar forms and intraspecific polychromatism present challenges for the taxonomy of some of these groups. Several species complexes have a largely unknown origin and unresolved evolutionary processes. Dwarf cichlids of the genus Apistogramma, comprising more than a hundred species, exhibit intricate taxonomic and biogeographic patterns, with both allopatric and sympatric distributions. However, karyotype evolution and the role of chromosomal changes in Apistogramma are still unknown. In the present study, nine South American Apistogramma species were analyzed using conventional cytogenetic methods and the mapping of repetitive DNA sequences [18S rDNA, 5S rDNA, and (TTAGGG)n] by fluorescence in situ hybridization (FISH). Our results showed that Apistogramma has unique cytogenetic characteristics in relation to closely related groups, such as a reduced 2n and a large number of bi-armed chromosomes. Interspecific patterns revealed a scenario of remarkable karyotypic changes, including a reduction of 2n, the occurrence of B-chromosomes and evolutionary dynamic of rDNA tandem repeats. In addition to the well-known pre-zygotic reproductive isolation, the karyotype reorganization in the genus suggests that chromosomal changes could act as postzygotic barriers in areas where Apistogramma congeners overlap.

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Distribution of Satellite DNA Sequences Isolated from Arctic Char, Salvelinus alpinus, in the Genus Salvelinus

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f94-314 ◽

1994 ◽

Vol 51 (S1) ◽

pp. 277-283 ◽

Cited By ~ 7

Author(s):

S. E. Hartley ◽

W. S. Davidson

Keyword(s):

Species Distribution ◽

Dna Sequences ◽

Satellite Dna ◽

Population Differentiation ◽

Genomic Dna ◽

Salvelinus Alpinus ◽

Arctic Char ◽

The Other ◽

Satellite Sequences ◽

Close Relationship

The distribution of satellite DNA sequences in the genus Salvelinus has been investigated by hybridization of four satellite DNA families isolated from Arctic char, Salvelinus alpinus, to the genomic DNA of S. alpinus, S. fontinalis, S. malma, S. namaycush, S. confluentus, and S. leucomaenis. The distribution of homologous AluI, DraI, and EcoRI satellite sequences suggests a close relationship between S. alpinus, S. malma, and S. confluentus with S. leucomaenis split from all the other species. S. namaycush has a closer relationship to the S. alpinus–malma–confluentus group than does S. fontinalis. The MboI satellite, which has potential as a marker for population differentiation in S. alpinus, has a species distribution suggestive of an ancient salmonid satellite that may have been lost from some species during transposition events.

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Features of Integration and Metaintegration in American Region

Rossijskoe Pravo. Obrazovanie, Praktika, Nauka ◽

10.34076/2410-2709-2019-1-58-64 ◽

2019 ◽

pp. 58-64

Keyword(s):

Integration Method ◽

South American ◽

Legal Systems ◽

Policy Integration ◽

American Continent ◽

Member States ◽

The Creation ◽

South American Continent ◽

Andean Community ◽

American Region

The analysis of integration of the legal systems of states in the American region is held. In the Southern subregion, a combination of integration and disintegration in cooperation of states led to the creation of two integration entities – MERCOSUR and the Andean Community (AC), in the Northern subregion – NAFTA. The author concludes that the convergence on the American continent, especially using the integration method, helped to implement a special scenario in the southern part of this continent – the meta-integration scenario, with the creation of the Union of South American Nations, uniting the Andean Community and MERCOSUR – something resembling a European one, but at the same time different from it. UNASUR is an effective mechanism for bringing together and integrating the states of the South American continent. Within this Union with notable leadership of Brazil and Argentina the first steps in the direction of the foreign policy integration of the member states are traced. In terms of economic integration, the Union uses the achievements of the AC and MERCOSUR, unifying the legal regulators in the economic sphere and bringing rapprochement to the legal systems of the member states.

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SPATIOTEMPORAL VARIABILITY OF PHOTOSYNTHETIC SENSITIVITY TO WATER AND RADIATION IN SOUTH AMERICAN CONTINENT

Journal of Japan Society of Civil Engineers Ser B1 (Hydraulic Engineering) ◽

10.2208/jscejhe.75.2_i_1117 ◽

2019 ◽

Vol 75 (2) ◽

pp. I_1117-I_1122

Author(s):

Shintaro FUJIMORI ◽

Hyungjun KIM

Keyword(s):

Spatiotemporal Variability ◽

South American ◽

American Continent ◽

South American Continent

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Effects of the diploidisation process upon the 5S and 35S rDNA sequences in the allopolyploid species of the Dilatata group of Paspalum (Poaceae, Paniceae)

Australian Journal of Botany ◽

10.1071/bt18236 ◽

2019 ◽

Vol 67 (7) ◽

pp. 521

Author(s):

Magdalena Vaio ◽

Cristina Mazzella ◽

Marcelo Guerra ◽

Pablo Speranza

Keyword(s):

Evolutionary Dynamics ◽

In Situ Hybridisation ◽

5S Rdna ◽

Its Region ◽

Variable Number ◽

Rrna Genes ◽

Fluorescence In Situ Hybridisation ◽

Rdna Sites ◽

35S Rdna ◽

Genome Restructuring

The Dilatata group of Paspalum includes species and biotypes native to temperate South America. Among them, five sexual allotetraploids (x = 10) share the same IIJJ genome formula: P. urvillei Steud, P. dasypleurum Kunze ex Desv., P. dilatatum subsp. flavescens Roseng., B.R. Arrill. & Izag., and two biotypes P. dilatatum Vacaria and P. dilatatum Virasoro. Previous studies suggested P. intermedium Munro ex Morong & Britton and P. juergensii Hack. or related species as their putative progenitors and donors of the I and J genome, respectively, and pointed to a narrow genetic base for their maternal origin. It has not yet been established whether the various members of the Dilatata group are the result of a single or of multiple allopolyploid formations. Here, we aimed to study the evolutionary dynamics of rRNA genes after allopolyploidisation in the Dilatata group of Paspalum and shed some light into the genome restructuring of the tetraploid taxa with the same genome formula. We used double target fluorescence in situ hybridisation of 35S and 5S rDNA probes and sequenced the nrDNA internal transcribed spacer (ITS) region. A variable number of loci at the chromosome ends were observed for the 35S rDNA, from 2 to 6, suggesting gain and loss of sites. For the 5S rDNA, only one centromeric pair of signals was observed, indicating a remarkable loss after polyploidisation. All ITS sequences generated were near identical to the one found for P. intermedium. Although sequences showed a directional homogeneisation towards the putative paternal progenitor in all tetraploid species, the observed differences in the number and loss of rDNA sites suggest independent ongoing diploidisation processes in all taxa and genome restructuring following polyploidy.

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Trance and Shamanic Cure on the South American Continent: Psychopharmacological and Neurobiological Interpretations

Anthropology of Consciousness ◽

10.1111/j.1556-3537.2010.01022.x ◽

2010 ◽

Vol 21 (1) ◽

pp. 83-105 ◽

Cited By ~ 4

Author(s):

FRANCOIS BLANC

Keyword(s):

South American ◽

American Continent ◽

The South ◽

South American Continent

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Molecular evolution of homologous gene sequences in germline-limited and somatic chromosomes of Acricotopus

Genome ◽

10.1139/g04-026 ◽

2004 ◽

Vol 47 (4) ◽

pp. 732-741 ◽

Cited By ~ 2

Author(s):

Wolfgang Staiber

Keyword(s):

Molecular Evolution ◽

Dna Sequences ◽

Sequence Data ◽

Structural Evolution ◽

5S Rdna ◽

Oligonucleotide Primer ◽

Homologous Gene ◽

Gene Sequences ◽

Nucleotide Substitutions ◽

Degenerate Oligonucleotide

The origin of germline-limited chromosomes (Ks) as descendants of somatic chromosomes (Ss) and their structural evolution was recently elucidated in the chironomid Acricotopus. The Ks consist of large S-homologous sections and of heterochromatic segments containing germline-specific, highly repetitive DNA sequences. Less is known about the molecular evolution and features of the sequences in the S-homologous K sections. More information about this was received by comparing homologous gene sequences of Ks and Ss. Genes for 5.8S, 18S, 28S, and 5S ribosomal RNA were choosen for the comparison and therefore isolated first by PCR from somatic DNA of Acricotopus and sequenced. Specific K DNA was collected by microdissection of monopolar moving K complements from differential gonial mitoses and was then amplified by degenerate oligonucleotide primer (DOP)-PCR. With the sequence data of the somatic rDNAs, the homologous 5.8S and 5S rDNA sequences were isolated by PCR from the DOP-PCR sequence pool of the Ks. In addition, a number of K DOP-PCR sequences were directly cloned and analysed. One K clone contained a section of a putative N-acetyltransferase gene. Compared with its homolog from the Ss, the sequence exhibited few nucleotide substitutions (99.2% sequence identity). The same was true for the 5.8S and 5S sequences from Ss and Ks (97.5%100% identity). This supports the idea that the S-homologous K sequences may be conserved and do not evolve independently from their somatic homologs. Possible mechanisms effecting such conservation of S-derived sequences in the Ks are discussed.Key words: microdissection, DOP-PCR, germline-limited chromosomes, molecular evolution.

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