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.

Sequential silver staining and in situ hybridization reveal a direct association between rDNA levels and the expression of homologous nucleolar organizing regions: a hypothesis for NOR structure and function

1998 ◽  
Vol 111 (10) ◽  
pp. 1433-1439
Author(s):  
F. Zurita ◽  
R. Jimenez ◽  
M. Burgos ◽  
R.D. de la Guardia
Keyword(s):  
Transcription Factors ◽  
In Situ Hybridization ◽  
Silver Staining ◽  
Organizer Region ◽  
Nucleolar Organizer ◽  
Interindividual Variation ◽  
Nucleolar Organizer Regions ◽  
Single Pair ◽  
Ribosomal Cistrons

We have developed a procedure for sequential silver staining and in situ hybridization to analyze the relationship between the amount of rDNA present in nucleolar organizer regions, as estimated by in situ hybridization, and their level of expression, as estimated by the silver signal. For simplicity we used cells from the insectivorous mole Talpa occidentalis, which have a single pair of nucleolar organizer regions in chromosome pair 3. The relative content of ribosomal cistrons was also related to the hierarchy of activation of the nucleolar organizer regions present in this chromosomal pair. Statistical analyses demonstrated that both the relative level of expression and the activation hierarchy depended mainly on the number of ribosomal cistrons in nucleolar organizer regions. We propose a functional two-step hypothesis, which is consistent with most known data concerning interchromosomal, intercellular and interindividual variation in a number of plant and animal species, including Talpa occidentalis. In step one, the first available transcription factors bind randomly to the ribosomal promoters, such that larger nucleolar organizer regions are more likely to recruit them. In the second step the remaining transcription factors are recruited in a cooperative way, thus completing activation of one nucleolar organizer region, before the next one becomes active.

Comparative cytogenetic analysis of Avena macrostachya and diploid C-genome Avena species

Genome ◽  
2010 ◽  
Vol 53 (2) ◽  
pp. 125-137 ◽  
Author(s):  
Ekaterina D. Badaeva ◽  
Olga Yu. Shelukhina ◽  
Axel Diederichsen ◽  
Igor G. Loskutov ◽  
Vitaly A. Pukhalskiy
Keyword(s):  
5S Rdna ◽  
Nucleolar Organizer ◽  
Nucleolar Organizer Regions ◽  
Rrna Gene ◽  
Avena Species ◽  
Rdna Sites ◽  
C Genome ◽  
Genome Group ◽  
26S Rrna

The chromosome set of Avena macrostachya Balansa ex Coss. et Durieu was analyzed using C-banding and fluorescence in situ hybridization with 5S and 18S-5.8S-26S rRNA gene probes, and the results were compared with the C-genome diploid Avena L. species. The location of major nucleolar organizer regions and 5S rDNA sites on different chromosomes confirmed the affiliation of A. macrostachya with the C-genome group. However, the symmetric karyotype, the absence of “diffuse heterochromatin”, and the location of large C-band complexes in proximal chromosome regions pointed to an isolated position of A. macrostachya from other Avena species. Based on the distribution of rDNA loci on the C-genome chromosomes of diploid and polyploid Avena species, we propose a model of the chromosome alterations that occurred during the evolution of oat species.

scholarly journals Cytogenetics of two sympatric Corydoras species (pisces, siluriformes, challichtyidae) of Southern Brazil

2006 ◽  
Vol 66 (1b) ◽  
pp. 191-198 ◽  
Author(s):  
R. F. Artoni ◽  
M. L. Terêncio ◽  
M. R. Vicari ◽  
M. C. A. Matiello ◽  
M. M. Cestari ◽  
...  
Keyword(s):  
In Situ Hybridization ◽  
Diploid Number ◽  
Constitutive Heterochromatin ◽  
Nucleolar Organizer ◽  
Nucleolar Organizer Regions ◽  
Great Similarity ◽  
Southern Brazil ◽  
Rdna Probe ◽  
Karyotypic Formula

Karyotypic data are presented for two sympatric Corydoras species of the Lagoa Dourada, namely, C. ehrhadti and C. paleatus, which are found in the upper Tibagi river basin (Ponta Grossa, State of Paraná, Brazil). The same diploid number and karyotypic formula were observed in both species/populations. A great similarity in the constitutive heterochromatin distribution and in the activity of nucleolar organizer regions was also found. The use of in situ hybridization with a fluorescent 18S rDNA probe allowed for the identification of the species/populations through the location of ribosomal sites.

Distribution of 45S rDNA in Modern Rose Cultivars (Rosa hybrida), Rosa rugosa, and Their Interspecific Hybrids Revealed by Fluorescence in situ Hybridization

2016 ◽  
Vol 149 (3) ◽  
pp. 226-235 ◽  
Author(s):  
Xiao-Liu Ding ◽  
Ting-Liang Xu ◽  
Jing Wang ◽  
Le Luo ◽  
Chao Yu ◽  
...  
Keyword(s):  
In Situ Hybridization ◽  
Fluorescence In Situ Hybridization ◽  
Interspecific Hybrids ◽  
Evolutionary Dynamics ◽  
The Other ◽  
45S Rdna ◽  
Expected Number ◽  
Rdna Sites ◽  
Rdna Loci

To elucidate the evolutionary dynamics of the location and number of rDNA loci in the process of polyploidization in the genus Rosa, we examined 45S rDNA sites in the chromosomes of 6 modern rose cultivars (R. hybrida), 5 R. rugosa cultivars, and 20 hybrid progenies by fluorescence in situ hybridization. Variation in the number of rDNA sites in parents and their interspecific hybrids was detected. As expected, 4 rDNA sites were observed in the genomes of 4 modern rose cultivars, while 3 hybridization sites were observed in the 2 others. Two expected rDNA sites were found in 2 R. rugosa cultivars, while in the other 3 R. rugosa cultivars 4 sites were present. Among the 20 R. hybrida × R. rugosa offspring, 13 carried the expected number of rDNA sites, and 1 had 6 hybridization sites, which exceeded the expected number by far. The other 6 offspring had either 2 or 3 hybridization sites, which was less than expected. Differences in the number of rDNA loci were observed in interspecific offspring, indicating that rDNA loci exhibit instability after distant hybridization events. Abnormal chromosome pairing may be the main factor explaining the variation in rDNA sites during polyploidization.

Chromosomal and genomic organization of Ty1-copia-like retrotransposon sequences in the genus Avena

Genome ◽  
1996 ◽  
Vol 39 (2) ◽  
pp. 410-417 ◽  
Author(s):  
A. Katsiotis ◽  
T. Schmidt ◽  
J. S. Heslop-Harrison
Keyword(s):  
In Situ Hybridization ◽  
Repetitive Sequence ◽  
Genomic Library ◽  
Nucleolar Organizer ◽  
Nucleolar Organizer Regions ◽  
Reaction Products ◽  
D Genome ◽  
Avena Species ◽  
Copy Numbers

A cloned repetitive sequence, pAvKB30, obtained from an Avena vaviloviana (AB genome) genomic library, along with two polymerase chain reaction products derived from the conserved region of the reverse transcriptase (RT) gene of retrotransposons, were characterized molecularly and cytologically. The cloned DNA fragment was a dispersed repeat present in all Avena species used in this study (A. strigosa, A. clauda, A. vaviloviana, A. magna, and A. sativa). The fragment was sequenced (210 bp) and found to be 69.5% homologous to part of WIS-2-1A, and 60.5% homologous to the leader sequence of BARE-1; both of these elements have been characterized as Ty1-copia-like retrotransposons in wheat and barley, respectively. In situ hybridization of pAvKB30 to diploid, tetraploid, and hexaploid oat species revealed that the probe is present on both arms of all chromosomes (A, B, C, and D genomes) but is excluded from their centromeric and nucleolar organizer regions. By using double in situ hybridization in hexaploid A. sativa (ACD genome), pAvKB30 was found to be present in lower copy numbers in C-genome chromosomes compared with A- and D-genome chromosomes. Furthermore, under low stringency conditions, pAvKB30 hybridized on Southern blots containing barley, wheat, rye, and Arrhenatherum DNA. However, under high stringency conditions, it hybridized only on Arrhenatherum DNA, which is considered to be the genus most closely related to Avena. All Avena species included in this study yielded a PCR product when the primers from the RT domain of retrotransposons were used. Two products, rtA, obtained by using A. strigosa (As genome) as template, and rtC, obtained by using A. clauda (Cp genome) as template, gave Southern and in situ hybridization results similar to pAvKB30, but each was more abundant in its genome of origin. Key words : genomes, oats, in situ hybridization, translocations, repetitive sequence.

Cyto-evolution of Boronia genomes revealed by fluorescent in situ hybridization with rDNA probes

Genome ◽  
2003 ◽  
Vol 46 (3) ◽  
pp. 507-513 ◽  
Author(s):  
Fucheng Shan ◽  
Guijun Yan ◽  
Julie A Plummer
Keyword(s):  
Fluorescent In Situ Hybridization ◽  
Diploid Species ◽  
Nucleolar Organizer ◽  
Nucleolar Organizer Regions ◽  
26S Rdna ◽  
Rdna Sequences ◽  
Gene Copies ◽  
Rdna Sites ◽  
Rdna Copy

The physical location of the 25S–26S rDNA sequences was examined in 11 taxa of nine species of Boronia. In diploid species, two rDNA sites were detected in Boronia clavata (2n = 14), Boronia pinnata 'White' (2n = 22), and Boronia chartacea (2n = 32); four in Boronia megastigma (2n = 14) and Boronia denticulata (2n = 18); six in Boronia pinnata 'Pink' (2n = 22); and eight in Boronia molloyae (2n = 16). Eleven sites were found in Boronia heterophylla 'Red' and 'Near White' (2n = 15), but only two active nucleolar organizer regions (NORs) were observed. In polyploid species, Boronia pilosa (2n = 44) had four rDNA sites, while Boronia coerulescens (2n = 72) had six. Most of the rDNA sequences were terminal, but a few were interstitial. There were also differences in signal intensity indicating that the gene copies between and within rDNA sites might be different. The result suggests that considerable chromosome rearrangements have occurred during Boronia cyto-evolution, leading to variation among Boronia taxa in rDNA copy number, site number, and location. These changes together with dysploid reduction during cyto-evolution have made the Boronia genome considerably diverse in chromosome number, genome organization, and chromosome structure.Key words: physical mapping, FISH, chromosome, Rutaceae.

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 Mapping 18S ribosomal genes in fish of the genus Brycon (Characidae) by fluorescence in situ hybridization (FISH)

2000 ◽  
Vol 23 (1) ◽  
pp. 135-138 ◽  
Author(s):  
Adriane Pinto Wasko ◽  
Pedro Manoel Galetti Jr.
Keyword(s):  
In Situ Hybridization ◽  
Fluorescence In Situ Hybridization ◽  
Nucleolar Organizer ◽  
Rrna Genes ◽  
Nucleolar Organizer Regions ◽  
Single Chromosome ◽  
Individual Variations ◽  
18S Rrna Genes ◽  
High Level

The present study provides data on the nucleolar organizer regions (NORs) of seven Brycon species based on mapping of the 18S rRNA genes by fluorescence in situ hybridization (FISH). Fluorescent signals were observed on the telomere of the long arm of two large submetacentric chromosomes, thus confirming the number and location of NORs previously revealed by other classical cytogenetic techniques. Although there were no inter- or intra-individual variations in the number and location of the 18S loci, NOR size polymorphism was observed between homologous chromosomes. The clustering and conservation of NORs in a single chromosome pair indicates a high level of NOR stability among species of the genus Brycon.

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