Cytogenetic evidence of nucleolar dominance in allotetraploid species of Brachypodium

Genome ◽  
2008 ◽  
Vol 51 (5) ◽  
pp. 387-391 ◽  
Author(s):  
Dominika Idziak ◽  
Robert Hasterok
Keyword(s):  
Nuclear Dna ◽  
Genomic Library ◽  
Diploid Species ◽  
Rrna Genes ◽  
Root Tip ◽  
45S Rdna ◽  
Bac Clone ◽  
Nucleolar Dominance ◽  
Rdna Sites ◽  
Cytogenetic Evidence

Sequential silver staining and fluorescence in situ hybridization (FISH) were used to establish activity and number of 45S rDNA sites in meristematic root tip cells of 6 ecotypes of allotetraploid (2n = 4x = 30) species of Brachypodium and their putative ancestors, B. distachyon (2n = 2x = 10) and ABR114 (2n = 2x = 20). Using either total nuclear DNA of ABR114 or the ABR1-63-E6 BAC clone from a B. distachyon genomic library as an auxiliary probe, it was possible to distinguish by FISH between the two genomes composing the ecotypes of allotetraploid Brachypodium species and to determine unambiguously the parentage of both dominant and suppressed rRNA genes. Each of the diploid species possessed two rDNA loci, both transcriptionally active. The number of 45S rDNA sites in 6 ecotypes of allotetraploid Brachypodium species was always equal to the sum of loci present in their putative diploid parents. Two smaller sites were located in chromosomes corresponding to the ABR114 chromosomal set, and two larger ones in the chromosomes of B. distachyon origin. In all analyzed allotetraploid ecotypes, only rRNA genes belonging to the B. distachyon–like genome were transcriptionally active, while rDNA from the other parental genome was always suppressed. Thus the occurrence of nucleolar dominance in the allotetraploid (2n = 4x = 30) species of Brachypodium is demonstrated for the first time.

Divergence between C. melo and African Cucumis Species Identified by Chromosome Painting and rDNA Distribution Pattern

2016 ◽  
Vol 150 (2) ◽  
pp. 150-155 ◽  
Author(s):  
Kunpeng Li ◽  
Huaisong Wang ◽  
Jiming Wang ◽  
Jianying Sun ◽  
Zongyun Li ◽  
...  
Keyword(s):  
Diploid Species ◽  
Distribution Patterns ◽  
45S Rdna ◽  
Rdna Sites ◽  
Cucumis Species ◽  
Cytogenetic Evidence ◽  
Rdna Fish ◽  
5S And 45S Rdna ◽  
Painting Probes

The 5S and 45S rDNA sites are useful chromosome landmarks and can provide valuable information about karyotype evolution and species interrelationships. In this study, we employed fluorescence in situ hybridization (FISH) to determine the number and chromosomal location of 5S and 45S rDNA loci in 8 diploid Cucumis species. Two oligonucleotide painting probes specific for the rDNA-bearing chromosomes in C. melo were hybridized to other Cucumis species in order to investigate the homeologies among the rDNA-carrying chromosomes in Cucumis species. The analyzed diploid species showed 3 types of rDNA distribution patterns, which provided clear cytogenetic evidence on the divergence between C. melo and wild diploid African Cucumis species. The present results not only show species interrelationships in the genus Cucumis, but the rDNA FISH patterns can also be used as cytological markers for the discrimination of closely related species. The data will be helpful for breeders to choose the most suitable species from various wild species for improvement of cultivated melon.

Genetic control of 1R nucleolus organizer region expression in the presence of wheat genomes

Genome ◽  
1990 ◽  
Vol 33 (5) ◽  
pp. 713-718 ◽  
Author(s):  
Rita Vieira ◽  
Álvaro Queiroz ◽  
Leonor Morais ◽  
Augusta Barão ◽  
T. Mello-Sampayo ◽  
...  
Keyword(s):  
Genetic Control ◽  
Hexaploid Wheat ◽  
Organizer Region ◽  
Nucleolus Organizer Region ◽  
Nucleolus Organizer ◽  
Rrna Genes ◽  
Root Tip ◽  
Region Gene ◽  
Nucleolar Dominance ◽  
Chromosome 1R

The expression of rRNA genes located in the nucleolar organizing region (NOR) present on the short arm of chromosome 1R from rye (Secale cereale L.) was examined in several hexaploid (Triticum aestivum L.) and tetraploid wheats (Triticum turgidum L.) containing the entire chromosome 1R from rye (disomic substitution 1B(1R)), its full haploid genome (hexaploid wheat–rye F1 hybrid), or only its short arm translocated to the long arms of wheat chromosomes from the homoeologous group 1 (disomic translocations 1AL/1RS, 1BL/1RS, or 1DL/1RS) or added to the complete hexaploid wheat genotype (monotelosomic addition 1RS). By silver staining and determination of the number of Ag-NORs and the average number of nucleoli per root-tip cell it became apparent that the expression of 1R NORs, in the presence of wheat genomes, depends on the absence of the long arm of rye chromosome 1R. In wheat-rye F1 hybrids and in hexaploid wheat with a disomic substitution 1B(1R), 1R NOR was morphologically absent, even when only one wheat major NOR was present, in contrast with its frequent expression in wheat–rye translocation or addition lines where only its short arm was added. It is suggested that wheat nucleolar dominance over rye as expressed by heterochromatic and silent NOR in 1RS is under a complex genetic control which involves interaction between 1RL and unidentified wheat genes.Key words: 1R nucleolus organizer region, gene activity, amphiplasty.

scholarly journals Analyses of the Updated “Animal rDNA Loci Database” with an Emphasis on Its New Features

2021 ◽  
Vol 22 (21) ◽  
pp. 11403
Author(s):  
Jana Sochorová ◽  
Francisco Gálvez ◽  
Roman Matyášek ◽  
Sònia Garcia ◽  
Aleš Kovařík
Keyword(s):  
Sex Chromosomes ◽  
5S Rdna ◽  
High Variability ◽  
Rrna Genes ◽  
45S Rdna ◽  
Data Analyses ◽  
Rdna Sites ◽  
Rdna Loci ◽  
Staining Methods ◽  
Active Nors

We report on a major update to the animal rDNA loci database, which now contains cytogenetic information for 45S and 5S rDNA loci in more than 2600 and 1000 species, respectively. The data analyses show the following: (i) A high variability in 5S and 45S loci numbers, with both showing 50-fold or higher variability. However, karyotypes with an extremely high number of loci were rare, and medians generally converged to two 5S sites and two 45S rDNA sites per diploid genome. No relationship was observed between the number of 5S and 45S loci. (ii) The position of 45S rDNA on sex chromosomes was relatively frequent in some groups, particularly in arthropods (14% of karyotypes). Furthermore, 45S rDNA was almost exclusively located in microchromosomes when these were present (in birds and reptiles). (iii) The proportion of active NORs (positively stained with silver staining methods) progressively decreased with an increasing number of 45S rDNA loci, and karyotypes with more than 12 loci showed, on average, less than 40% of active loci. In conclusion, the updated version of the database provides some new insights into the organization of rRNA genes in chromosomes. We expect that its updated content will be useful for taxonomists, comparative cytogeneticists, and evolutionary biologists. 

Chromosomal Mapping of Repeat DNA in Bergiaria westermanni (Pimelodidae, Siluriformes): Localization of 45S rDNA in B Chromosomes

2018 ◽  
Vol 154 (2) ◽  
pp. 99-106 ◽  
Author(s):  
Geovana C. Malimpensa ◽  
Josiane B. Traldi ◽  
Danyelle Toyama ◽  
Flávio Henrique-Silva ◽  
Marcelo R. Vicari ◽  
...  
Keyword(s):  
Chromosomal Rearrangements ◽  
Indirect Evidence ◽  
5S Rdna ◽  
B Chromosomes ◽  
Chromosomal Mapping ◽  
Interindividual Variation ◽  
Rrna Genes ◽  
45S Rdna ◽  
Rdna Sites ◽  
Repeat Dna

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.

Cytological studies of the nucleolus organizing regions in the Medicago complex: sativa–coerulea–falcata

Genome ◽  
1996 ◽  
Vol 39 (5) ◽  
pp. 914-920 ◽  
Author(s):  
O. Calderini ◽  
F. Pupilli ◽  
P. D. Cluster ◽  
A. Mariani ◽  
S. Arcioni
Keyword(s):  
In Situ Hybridization ◽  
Silver Nitrate ◽  
Fluorescent In Situ Hybridization ◽  
Diploid Species ◽  
2N Gametes ◽  
Root Tip ◽  
Medicago Falcata ◽  
Rdna Sites ◽  
Silver Nitrate Staining

A cytological examination of the nucleolus organizing regions (NORs) of three species from the Medicago sativa complex was conducted to evaluate the structural and functional evolution of the ribosomal RNA (rRNA) loci that encode the 18S, 5.8S, and 26S rRNAs. Mitotic chromosomes in root-tip preparations from tetraploid M. sativa and diploids Medicago coerulea and Medicago falcata were visualized by four methods that provide new data. Fluorescent in situ hybridization using the M. sativa 18S gene as probe localized the structural rDNA to the constricted regions of the satellited chromosomes only. Chromomycin A3 (CMA3) staining and 4′,6-diamidino-2-phenylindole (DAPI) staining identified these chromosomal segments as the most GC-rich regions in the alfalfa karyotype. Medicago falcata exhibited fewer DAPI bands and chromocenters than did M. sativa and M. coerulea. Positive silver nitrate staining showed that all four rDNA regions in M. sativa (located in two chromosome pairs) and both rDNA sites in both diploid species remain transcriptionally active. Counts of nucleoli confirmed that all rDNA regions are independently capable of nucleolus organization. Thus, the number of active NORs in M. sativa is double the number found in M. coerulea or M. falcata. Consequently, if M. sativa originated from sexual hybridization of 2n gametes involving one or both diploid species, no major reorganization or loss of structural or functional rDNA loci has occurred. Key words : alfalfa evolution, CMA3 banding, DAPI banding, fluorescent in situ hybridization, silver nitrate staining.

scholarly journals Nucleolar dominance and maternal control of 45S rDNA expression

2015 ◽  
Vol 282 (1820) ◽  
pp. 20152201 ◽  
Author(s):  
Katarzyna Michalak ◽  
Sebastian Maciak ◽  
Young Bun Kim ◽  
Graciela Santopietro ◽  
Jung Hun Oh ◽  
...  
Keyword(s):  
Sex Chromosome ◽  
De Novo ◽  
Rrna Genes ◽  
Rrna Gene ◽  
Messenger Rnas ◽  
45S Rdna ◽  
Maternal Control ◽  
Nucleolar Dominance ◽  
Gene Copies ◽  
Rdna Expression

Using a system of interspecies hybrids, trihybrids, and recombinants with varying proportions of genomes from three distinct Xenopus species, we provide evidence for de novo epigenetic silencing of paternal 45S ribosomal ribonucleic acid (rRNA) genes and their species-dependent expression dominance that escapes transcriptional inactivation after homologous recombination. The same pattern of imprinting is maintained in the offspring from mothers being genetic males (ZZ) sex-reversed to females, indicating that maternal control of ribosomal deoxyribonucleic acid (rDNA) expression is not sex-chromosome linked. Nucleolar dominance (nucleolus underdevelopment) in Xenopus hybrids appears to be associated with a major non-Mendelian reduction in the number of 45S rDNA gene copies rather than a specific pattern of their expression. The loss of rRNA gene copies in F 1 hybrids was non-random with respect to the parental species, with the transcriptionally dominant variant preferentially removed from hybrid zygotes. This dramatic disruption in the structure and function of 45S rDNA impacts transcriptome patterns of small nucleolar RNAs and messenger RNAs, with genes from the ribosome and oxidative stress pathways being among the most affected. Unorthodoxies of rDNA inheritance and expression may be interpreted as hallmarks of genetic conflicts between parental genomes, as well as defensive epigenetic mechanisms employed to restore genome integrity.

THE 4C NUCLEAR DNA CONTENT OF SEVERAL HORDEUM GENOTYPES

1971 ◽  
Vol 13 (3) ◽  
pp. 607-611 ◽  
Author(s):  
Michael D. Bennett ◽  
J. B. Smith
Keyword(s):  
Dna Content ◽  
Nuclear Dna ◽  
Geographical Origin ◽  
Diploid Species ◽  
Nuclear Dna Content ◽  
Root Tip ◽  
Dna Contents ◽  
Hordeum Species ◽  
Nuclear Dna Contents ◽  
Physiological Characters

The 4C nuclear DNA content was estimated for 17 wild Hordeum species and five cultivated Hordeum vulgare varieties which were chosen to include examples varying greatly in geographical origin and in morphological and physiological characters. Nuclear DNA was measured on an integrating microdensitometer using prophase nuclei in Feulgen stained root-tip squashes. There were no significant differences in DNA content between any or the 15 diploid genotypes measured, and the seven polyploid genotypes all had nuclear DNA contents which were simple multiples of the diploid genotypes. This result, namely that the DNA content of diploid Hordeum species is invariable, differs from results obtained from diploid species in several other plant genera which differed greatly in nuclear DNA content.

1R chromosome nucleolus organizer region activation by 5-azacytidine in wheat × rye hybrids

Genome ◽  
1990 ◽  
Vol 33 (5) ◽  
pp. 707-712 ◽  
Author(s):  
Rita Vieira ◽  
Álvaro Queiroz ◽  
Leonor Morais ◽  
Augusta Barão ◽  
T. Mello-Sampayo ◽  
...  
Keyword(s):  
Triticum Turgidum ◽  
Organizer Region ◽  
Nucleolus Organizer Region ◽  
Nucleolar Organizer ◽  
Pyrimidine Ring ◽  
Nucleolus Organizer ◽  
Rrna Genes ◽  
Root Tip ◽  
Root Tips ◽  
Nucleolar Dominance

Nucleolar activity was studied in several lines of Triticum aestivum cv. Chinese Spring, Triticum turgidum cv. Durum, and F1 hybrids from euploid and aneuploid lines of T. aestivum and Secale cereale cv. Centeio do Alto, in cells from root tips of seeds germinated in water or in 5-azacytidine. 5-Azacytidine, an analog of cytidine modified in the 5 position of the pyrimidine ring, inhibits DNA methylation. By using silver staining to determine the number of nucleolus organizer regions and the average number of nucleoli per root-tip cell from seeds germinated in both situations, it became apparent that the presence of 5-azacytidine during germination allowed for the expression of the nucleolus organizer region locus belonging to the rye genome, in contrast to the usual observed cytological absence of the rye nucleolus organizer region in wheat–rye hybrids. It is suggested that wheat nucleolar dominance in wheat–rye hybrids is mainly a consequence of methylation of rRNA genes or its regulators located on the 1R chromosome of rye.Key words: 1R nucleolar organizer, wheat–rye hybrids, methylation, Ag-NOR.

scholarly journals Simultaneous Visualization of 5S and 45S rDNAs in Persimmon (Diospyros kaki) and Several Wild Relatives (Diospyros spp.) by Fluorescent in situ Hybridization (FISH) and MultiColor FISH (MCFISH)

2003 ◽  
Vol 128 (5) ◽  
pp. 736-740 ◽  
Author(s):  
Young A Choi ◽  
Ryutaro Tao ◽  
Keizo Yonemori ◽  
Akira Sugiura
Keyword(s):  
Fluorescent In Situ Hybridization ◽  
Diploid Species ◽  
5S Rdna ◽  
Diospyros Kaki ◽  
45S Rdna ◽  
Multicolor Fish ◽  
Rdna Probe ◽  
Rdna Sites ◽  
5S And 45S Rdna

5S ribosomal DNA (rDNA) was visualized on the somatic metaphase chromosome of persimmon (Diospyros kaki) and ten wild Diospyros species by fluorescent in situ hybridization (FISH). The digoxigenin (DIG)-labeled 5S rDNA probe was hybridized onto the chromosomes and visualized by incubation with anti-DIG-fluorescein isothiocyanate (FITC). Strong signals of 5S rDNA probe were observed on several chromosomes of Diospyros species tested. Furthermore, multicolor FISH using 5S and 45S rDNA probes differently labeled with DIG and biotin, revealed separate localization of the two rDNA genes on different chromosomes of Diospyros species tested, suggesting that 5S and 45S rDNA sites can be used as chromosome markers in Diospyros. The number of 5S rDNA sites varied with the Diospyros species. More 5S rDNA sites were observed in four diploid species native to Southern Africa than in three Asian diploid species. The former had four or six 5S rDNA sites while the latter had two. Three Asian polyploidy species had four to eight 5S rDNA sites. Among the Asian species, the number of 5S rDNA sites seemed to increase according to ploidy level of species. These features of 5S rDNA sites were very similar to those of 45S rDNA sites in Diospyros. Phylogenetic relationship between D. kaki and wild species tested are discussed based on the number and chromosomal distribution of 5S and 45S rDNA.

Nucleolar dominance does not occur in root tip cells of allotetraploid Brassica species

Genome ◽  
2000 ◽  
Vol 43 (3) ◽  
pp. 574-579 ◽  
Author(s):  
Robert Hasterok ◽  
Jolanta Maluszynska
Keyword(s):  
In Situ Hybridization ◽  
Nucleolar Organizer ◽  
Brassica Species ◽  
Root Tip ◽  
Nucleolar Organizer Regions ◽  
Nucleolar Dominance ◽  
Rdna Sites ◽  
Rdna Loci ◽  
Allotetraploid Species

Using in situ hybridization and silver staining methods, the numbers of active and inactive rDNA loci have been established for three allotetraploid species of Brassica (B. napus, B. carinata, and B. juncea) and their diploid ancestors (B. campestris, B. nigra, and B. oleracea). The allotetraploid species have chromosome numbers equal to the sum of the numbers in their diploid relatives, but have fewer rDNA loci. All species investigated have lower numbers of active NORs (AgNORs, nucleolar organizer regions) compared with the numbers of rDNA sites revealed by in situ hybridization. The number of active rDNA loci of the allotetraploid species is equal to the number of AgNORs in their diploid ancestors, indicating the absence of nucleolar dominance in amphidiploid Brassica species, at least in root meristematic cells.Key words: AgNOR, Brassica, FISH, nucleolar dominance, rDNA.

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