Chromosomal Mapping of Repetitive DNAs in Gobionellus oceanicus and G. stomatus (Gobiidae; Perciformes): A Shared XX/XY System and an Unusual Distribution of 5S rDNA Sites on the Y Chromosome

The occurrence of repetitive DNA in autosomes and B chromosomes of Bergiaria westermanni was examined using conventional and molecular cytogenetic techniques. This species exhibited 2n = 56 chromosomes, with intra- and interindividual variation in the number of heterochromatic B chromosomes (from 0 to 4). The 5S rDNA was localized in pairs 1 and 5, and histone probes (H1, H3, and H4) and U2 small nuclear RNA were syntenic with 5S rDNA in pair 5. Histone sequences were also located in chromosome pair 14. The (GATA)n sequence was dispersed throughout the autosomes and B chromosomes, with clusters (microsatellite accumulation) in some chromosome regions. The telomeric probe revealed no signs of chromosomal rearrangements in the genome of B. westermanni. The 45S rDNA sites were detected in the terminal region of pair 27; these sites corresponded to a GC-rich heterochromatin block. In addition, 3 of the 4 B chromosomes also contained 45S rDNA copies. Silver nitrate staining in interphase nuclei provided indirect evidence of the expression of these rRNA genes in B chromosomes, indicating the probable origin of these elements. This report shows plasticity in the chromosomal localization of repeat DNA in B. westermanni and features a discussion of genomic diversification.

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Centric Fusions behind the Karyotype Evolution of Neotropical Nannostomus Pencilfishes (Characiforme, Lebiasinidae): First Insights from a Molecular Cytogenetic Perspective

Genes ◽

10.3390/genes11010091 ◽

2020 ◽

Vol 11 (1) ◽

pp. 91 ◽

Cited By ~ 5

Author(s):

Alexandr Sember ◽

Ezequiel Aguiar de Oliveira ◽

Petr Ráb ◽

Luiz Antonio Carlos Bertollo ◽

Natália Lourenço de Freitas ◽

...

Keyword(s):

Repetitive Dna ◽

Small Body ◽

5S Rdna ◽

Chromosomal Mapping ◽

Comparative Genomic ◽

Comparative Genome Hybridization ◽

Body Coloration ◽

Rdna Sites ◽

Karyotype Differentiation ◽

Conventional Cytogenetics

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.

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Chromosomal Mapping of 18S-25S and 5S Ribosomal Genes on 15 Species of Fagaceae From Northern Thailand

Silvae Genetica ◽

10.1515/sg-2008-0002 ◽

2008 ◽

Vol 57 (1-6) ◽

pp. 5-13 ◽

Cited By ~ 12

Author(s):

P. Chokchaichamnankit ◽

K. Anamthawat-Jónsson ◽

W. Chulalaksananukul

Keyword(s):

In Situ Hybridisation ◽

5S Rdna ◽

Ribosomal Genes ◽

Chromosomal Mapping ◽

Hybrid Origin ◽

Fluorescence In Situ Hybridisation ◽

Northern Thailand ◽

Quercus Species ◽

Rdna Sites ◽

25S Rdna

Abstract Fifteen species of Fagaceae from Chiang Mai province, northern Thailand, were investigated: eight Castanopsis, four Lithocarpus and three Quercus species. The species were generally diploid with the chromosome number 2n = 24, and the basic number x =12 was confirmed in some species with meiosis. One tree belonging to Q. lenticellatus had 2n = 14. Chromosomal mapping of the highly repetitive 18S-25S and 5S ribosomal genes by fluorescence in situ hybridisation (FISH) was performed. Most species (from all three genera) showed four 18S-25S rDNA sites (two pairs: one subterminal major and one paracentromeric/intercalary minor loci) and two 5S rDNA sites (one pair: paracentromeric locus). Quercus kerrii also had two pairs of 18S-25S rDNA sites, but both were subterminal major loci. Two species, C. argentea and Q. brandisianus, only had one pair of 18S-25S rDNA sites. Two species, C. calathiformis and L. vestitus, showed an odd number of (unpaired) sites, and this indicated hybrid origin and/or polyploidy. Polyploid cells were detected in these species. The ribosomal gene maps based on both sequences together were genus-specific. In Castanopsis, the 18S-25S and the 5S genes were localized on three different chromosome pairs, and comprised species-specific maps. On the other hand, the ribosomal genes in Lithocarpus and Quercus were found only on two chromosome pairs, because one of the two 18S-25S rDNA loci was localized on the same chromosome as the 5S rDNA locus. The FISH markers may be used to clarify discrepancies arising from morphological assessments.

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Cytogenetic Analysis and Chromosomal Mapping of Repetitive DNA in Melipona Species (Hymenoptera, Meliponini)

Cytogenetic and Genome Research ◽

10.1159/000501754 ◽

2019 ◽

Vol 158 (4) ◽

pp. 213-224 ◽

Cited By ~ 5

Author(s):

Natália M. Travenzoli ◽

Bárbara A. Lima ◽

Danon C. Cardoso ◽

Jorge A. Dergam ◽

Tânia M. Fernandes-Salomão ◽

...

Keyword(s):

Stingless Bees ◽

Chromosome Evolution ◽

Repetitive Sequences ◽

Sensu Stricto ◽

Chromosomal Mapping ◽

Evolutionary Constraints ◽

Rdna Sites ◽

Melipona Species ◽

The Relationship ◽

Evolutionary Lineages

Stingless bees of the genus Melipona are subdivided into 4 subgenera called Eomelipona, Melikerria, Melipona sensu stricto, and Michmelia according to species morphology. Cytogenetically, the species of the genus Melipona show variation in the amount and distribution of heterochromatin along their chromosomes and can be separated into 2 groups: the first with low content of heterochromatin and the second with high content of heterochromatin. These heterochromatin patterns and the number of chromosomes are characteristics exclusive to Melipona karyotypes that distinguish them from the other genera of the Meliponini. To better understand the karyotype organization in Melipona and the relationship among the subgenera, we mapped repetitive sequences and analyzed previously reported cytogenetic data with the aim to identify cytogenetic markers to be used for investigating the phylogenetic relationships and chromosome evolution in the genus. In general, Melipona species have 2n = 18 chromosomes, and the species of each subgenus share the same characteristics in relation to heterochromatin regions, DAPI/CMA3 fluorophores, and the number and distribution of 18S rDNA sites. Microsatellites were observed only in euchromatin regions, whereas the (TTAGG)6 repeats were found at telomeric sites in both groups. Our data indicate that in addition to the chromosome number, the karyotypes in Melipona could be separated into 2 groups that are characterized by conserved cytogenetic features and patterns that generally are shared by species within each subgenus, which may reflect evolutionary constraints. Our results agree with the morphological separation of the Melipona into 4 subgenera, suggesting that they must be independent evolutionary lineages.

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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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Gene mapping of 5S rDNA sites in eight fish species from the Paraíba do Sul river basin, Brazil

Cytogenetic and Genome Research ◽

10.1159/000078567 ◽

2004 ◽

Vol 106 (1) ◽

pp. 107-110 ◽

Cited By ~ 47

Author(s):

K.F. Kavalco ◽

R. Pazza ◽

L.A.C. Bertollo ◽

O. Moreira-Filho

Keyword(s):

Gene Mapping ◽

River Basin ◽

Fish Species ◽

5S Rdna ◽

Rdna Sites ◽

Paraíba Do Sul River

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Paracentric Inversions Differentiate the Conservative Karyotypes in Two Centropomus Species (Teleostei: Centropomidae)

Cytogenetic and Genome Research ◽

10.1159/000499748 ◽

2019 ◽

Vol 157 (4) ◽

pp. 239-248 ◽

Cited By ~ 2

Author(s):

Amanda T. Borges ◽

Marcelo B. Cioffi ◽

Luiz A.C. Bertollo ◽

Rodrigo X. Soares ◽

Gideão W.W.F. Costa ◽

...

Keyword(s):

Economic Value ◽

5S Rdna ◽

Chromosomal Evolution ◽

Chromosomal Mapping ◽

Rdna Site ◽

Fluorochrome Staining ◽

Western Atlantic ◽

Replication Banding ◽

Evolutionary Diversification ◽

Paracentric Inversions

Centropomus is the sole genus of the Centropomidae family (Teleostei), comprising 12 species widely distributed throughout the Western Atlantic and Eastern Pacific, with 6 of them occurring in the Western Atlantic in extensive sympatry. Their life history and phylogenetic relationships are well characterized; however, aspects of chromosomal evolution are still unknown. Here, cytogenetic analyses of 2 Centropomus species of great economic value (C. undecimalis and C. mexicanus) were performed using conventional (Giemsa, Ag-NOR, and fluorochrome staining, C- and replication banding) and molecular (chromosomal mapping of 18S and 5S rDNA, H2A-H2B and H3 hisDNA, and (TTAGGG)n repeats) approaches. The karyotypes of both species were composed of 48 solely acrocentric chromosomes (2n = 48; FN = 48), but the single ribosomal site was located in varying positions in the long arms of the second largest chromosome pair. Replication bands were generally similar, although conspicuous differences were observed in some chromosome regions. In both species, the histone H3 genes were located on 3 apparently homeologous chromosome pairs, but the exact position of these clusters differed slightly. Interspecific hisDNA and rDNA site displacements can indicate the occurrence of multiple paracentric inversions during the evolutionary diversification of the Centropomus genomes. Although the karyotypes remained similar in both species, our data demonstrate an unsuspected microstructural reorganization between them, driven most likely by a series of paracentric inversions.

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Chromosomal mapping of repetitive sequences in Hyphessobrycon eques (Characiformes, Characidae): a special case of the spreading of 5S rDNA clusters in a genome

Genetica ◽

10.1007/s10709-020-00086-3 ◽

2020 ◽

Vol 148 (1) ◽

pp. 25-32 ◽

Cited By ~ 1

Author(s):

Diovani Piscor ◽

Leonardo Marcel Paiz ◽

Lucas Baumgärtner ◽

Fiorindo José Cerqueira ◽

Carlos Alexandre Fernandes ◽

...

Keyword(s):

Repetitive Sequences ◽

5S Rdna ◽

Chromosomal Mapping ◽

A Genome ◽

Special Case

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Sex Chromosomes and Internal Telomeric Sequences in Dormitator latifrons (Richardson 1844) (Eleotridae: Eleotrinae): An Insight into Their Origin in the Genus

Genes ◽

10.3390/genes11060659 ◽

2020 ◽

Vol 11 (6) ◽

pp. 659

Author(s):

Fabilene Gomes Paim ◽

Mauro Nirchio ◽

Claudio Oliveira ◽

Anna Rita Rossi

Keyword(s):

Sex Chromosomes ◽

Food Resource ◽

5S Rdna ◽

Molecular Techniques ◽

Chromosomal Mapping ◽

Nucleolar Organizer Regions ◽

Neotropical Fish ◽

Telomeric Repeats ◽

Western Atlantic ◽

Telomeric Sequences

The freshwater fish species Dormitator latifrons, commonly named the Pacific fat sleeper, is an important food resource in CentralSouth America, yet almost no genetic information on it is available. A cytogenetic analysis of this species was undertaken by standard and molecular techniques (chromosomal mapping of 18S rDNA, 5S rDNA, and telomeric repeats), aiming to describe the karyotype features, verify the presence of sex chromosomes described in congeneric species, and make inferences on chromosome evolution in the genus. The karyotype (2n = 46) is mainly composed of metacentric and submetacentic chromosomes, with nucleolar organizer regions (NORs) localized on the short arms of submetacentric pair 10. The presence of XX/XY sex chromosomes was observed, with the X chromosome carrying the 5S rDNA sequences. These heterochromosomes likely appeared before 1 million years ago, since they are shared with another derived Dormitator species (Dormitator maculatus) distributed in the Western Atlantic. Telomeric repeats hybridize to the terminal portions of almost all chromosomes; additional interstitial sites are present in the centromeric region, suggesting pericentromeric inversions as the main rearrangement mechanisms that has driven karyotypic evolution in the genus. The data provided here contribute to improving the cytogenetics knowledge of D. latifrons, offering basic information that could be useful in aquaculture farming of this neotropical fish.

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Molecular Cytogenetic Analysis of Karyotype and Y Chromosome Conservation in Species of the Genus Talpa (Insectivora)

Cytogenetic and Genome Research ◽

10.1159/000507836 ◽

2020 ◽

Vol 160 (5) ◽

pp. 264-271

Author(s):

Juana Gutierrez ◽

Gael Aleix-Mata ◽

Juan A. Marchal ◽

María Arroyo ◽

Riccardo Castiglia ◽

...

Keyword(s):

Sequence Analysis ◽

Y Chromosome ◽

Repetitive Dna ◽

Dna Sequences ◽

Chromosome Painting ◽

Chromosomal Mapping ◽

Repeated Dna ◽

Molecular Cytogenetic ◽

Y Chromosomes ◽

Cytogenetic Analyses

The Talpidae family has a highly stable karyotype. Most of the chromosome studies in this mammal group, however, employed classical cytogenetic techniques. Molecular cytogenetic analyses are still scarce and, for example, no repeated DNA sequences have been described to date. In this work, we used sequence analysis, chromosomal mapping of a LINE1 retroelement sequence, as well as chromosome painting with a whole Y chromosome probe of T. occidentalis to compare the karyotypes of 3 species of the genus Talpa (T. occidentalis, T. romana, and T. aquitania). Our results demonstrate that in Talpa genomes LINE1 sequences are widely distributed on all chromosomes but are enriched in pericentromeric C-band-positive regions. In addition, these LINE1 accumulate on the Y chromosomes of the 3 Talpa species regardless of their euchromatic or heterochromatic condition. Chromosome painting shows that the Y chromosomes in these 3 species are highly conserved. Interestingly, they share sequences with heterochromatic blocks on chromosome pairs 14 and 16 and, to a lesser degree, with the pericentromeric regions of other autosomes. Together, our analyses demonstrate that the repetitive DNA content of chromosomes from Talpa species is highly conserved.

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