Molecular cloning and characterization of an unusually large intergenic spacer from the Nor-B2 locus of hexaploid wheat

Genome ◽  
1996 ◽  
Vol 39 (2) ◽  
pp. 288-292 ◽  
Author(s):  
R. K. Sardana ◽  
R. B. Flavell
Keyword(s):  
Key Words ◽  
Ribosomal Dna ◽  
Hexaploid Wheat ◽  
Organizer Region ◽  
Nucleolar Organizer Region ◽  
Intergenic Spacer ◽  
Nucleolar Organizer ◽  
Spacer Length ◽  
Spacer Length Variants

An allelic rDNA variant from the Nor-B2 locus of 'Bezostaya' wheat that forms an especially active nucleolus was cloned and characterized. It carries an unusually large intergenic spacer compared with rDNA units in most other wheat genotypes. The additional intergenic length is in the array of 135-bp A repeats and not in other internal repeats. These A repeats have sequences nearly identical to other A repeats described for other alleles. It is suggested therefore that the more active Nor-B2 locus of 'Bezostaya' may be due to the constituent rDNA units possessing a larger array of A repeats. Key words : ribosomal DNA, nucleolar organizer region, A and B repeats, allelic, spacer length variants.

Alien chromatin in wheat: ribosomal DNA spacer probes for detecting specific nucleolar organizer region loci introduced into wheat

1986 ◽  
Vol 28 (5) ◽  
pp. 665-672 ◽  
Author(s):  
R. Appels ◽  
C. L. McIntyre ◽  
B. C. Clarke ◽  
C. E. May
Keyword(s):  
Restriction Endonuclease ◽  
Ribosomal Dna ◽  
Organizer Region ◽  
Nucleolar Organizer Region ◽  
Nucleolar Organizer ◽  
Molecular Probes ◽  
Restriction Endonuclease Mapping ◽  
Endonuclease Mapping ◽  
Alien Chromatin

The structure, at the level of restriction endonuclease mapping, of rDNA spacer regions from representatives of the B, R, S, P, N, J1J2, and E genomes within the Triticeae are compared. The results indicate that the evolution of the main spacer region of rDNA units is sufficiently rapid to allow each genome to be clearly identified. The spacer regions can be successfully used to distinguish respective alien rDNA units when they are present in wheat.Key words: Triticeae, alien chromatin, molecular probes, NOR loci.

Metaphase association of mammalian chromosomes

Genome ◽  
1987 ◽  
Vol 29 (6) ◽  
pp. 807-810
Author(s):  
U. Mayr-Wohlfart ◽  
S. Adolph ◽  
Ch. Klett ◽  
H. Hameister
Keyword(s):  
Key Words ◽  
Chromosomal Localization ◽  
Organizer Region ◽  
Nucleolar Organizer Region ◽  
Nucleolar Organizer ◽  
Association Behavior ◽  
Per Se ◽  
Ectopic Pairing

The association behavior of chromosomes bearing nucleolar organizer region (NOR) and (or) C-heterochromatin in metaphase plates was analyzed. Different species with an informative chromosomal localization of NOR and C-heterochromatin were evaluated. Several examples indicate that the well-known metaphase association is not due to NORs or NOR activity per se. Other mechanisms such as ectopic pairing are responsible for the association. These types of pairing seem to be enhanced by the chromatin-decondensing effect of nearby NOR activity. Key words: NOR, C-heterochromatin, metaphase association.

5S rDNA genome regions of Lens species

Genome ◽  
2005 ◽  
Vol 48 (5) ◽  
pp. 937-942 ◽  
Author(s):  
M Fernández ◽  
M L Ruiz ◽  
C Linares ◽  
A Fominaya ◽  
M Pérez de la Vega
Keyword(s):  
Lens Culinaris ◽  
Organizer Region ◽  
Nucleolar Organizer Region ◽  
Pcr Amplification ◽  
Intergenic Spacer ◽  
5S Rdna ◽  
Nucleolar Organizer ◽  
Repeated Sequence ◽  
Nontranscribed Spacer ◽  
Selective Hybridization

The length variability of the nontranscribed spacer (NTS) of the 5S rDNA repeats was analyzed in species of the genus Lens by means of PCR amplification. The NTS ranged from ~227 to ~952 bp. The polymorphism detected was higher than previous NTS polymorphisms described in this genus. Three NTS length variants from Lens culinaris subsp. culinaris and 2 from Lens culinaris subsp. orientalis were sequenced. The culinaris NTS fragment lengths were 239, 371, and 838 bp, whereas the orientalis ones were 472 bp and 506 bp, respectively. As a result of sequence similarities, 2 families of sequences were distinguished, 1 including the sequences of 838 and 506 bp, and others with the sequences of 239, 371, and 472 bp. The 1st family was characterized by the presence of a repeated sequence designated A, whereas the 2nd family showed a single A sequence and other repeated sequences designated B, C, and D. The presence of an (AT)n microsatellite was also observed in the 2nd family of sequences. The fragments, which included the 239-bp and 838-bp NTS sequences, as well as the intergenic spacer (IGS) of the 18S–5.8S–26S ribosomal DNA also from L. culinaris subsp. culinaris, were used to localize the nucleolar organizer region (NOR) and the 5S rDNA loci in the chromosomes of several species of the genus Lens by means of fluorescence in situ hybridization (FISH). The selective hybridization of the 2 NTS probes allowed us to distinguish between different 5S rDNA chromosomal loci.Key words: Lens, lentil, ribosomal loci, 5S, FISH, NTS polymorphism, NOR.

Pattern of nucleolar organizer region activity during male meiosis in Callicrania seoanei (Orthoptera) as analyzed by silver staining: evidences for a possible reactivation in the period between the two meiotic divisions

Genome ◽  
1987 ◽  
Vol 29 (3) ◽  
pp. 516-518 ◽  
Author(s):  
J. Santos ◽  
C. Sentis ◽  
J. Fernandez-Piqueras
Keyword(s):  
Key Words ◽  
Silver Staining ◽  
Transcriptional Activity ◽  
Organizer Region ◽  
Nucleolar Organizer Region ◽  
Nucleolar Organizer ◽  
Male Meiosis ◽  
Positive Material ◽  
Ribosomal Cistrons ◽  
Early Spermatid

Silver staining of spermatocytes and early spermatid nuclei from the neo XY race of the Tettigonioid species Callicrania seoanei reveals an active nucleolar organizer region (NOR) located proximally in a medium-sized bivalent. Ag-positive material was present at the NOR in all stages of male meiosis. However, the results obtained indicate that transcriptional activity of ribosomal cistrons (rDNA) is not maintained throughout spermatogenesis, but that NOR reactivation might occur in the period between the two meiotic divisions in addition to the more general postmeiotical reactivation in the early spermatid nuclei. Key words: NOR activity, silver staining, male meiosis, Callicrania seoanei (Orthoptera).

Hypervariability of ribosomal DNA at multiple chromosomal sites in lake trout (Salvelinus namaycush)

Genome ◽  
1995 ◽  
Vol 38 (3) ◽  
pp. 487-496 ◽  
Author(s):  
Lang Zhuo ◽  
Kent M. Reed ◽  
Ruth B. Phillips
Keyword(s):  
Repetitive Dna ◽  
Ribosomal Dna ◽  
Lake Trout ◽  
Organizer Region ◽  
Nucleolus Organizer Region ◽  
Intergenic Spacer ◽  
Salvelinus Namaycush ◽  
Coding Region ◽  
Spacer Length ◽  
Rdna Sites

Variation in the intergenic spacer (IGS) of the ribosomal DNA (rDNA) of lake trout (Salvelinus namaycush) was examined. Digestion of genomic DNA with restriction enzymes showed that almost every individual had a unique combination of length variants with most of this variation occurring within rather than between populations. Sequence analysis of a 2.3 kilobase (kb) EcoRI–DraI fragment spanning the 3′ end of the 28S coding region and approximately 1.8 kb of the IGS revealed two blocks of repetitive DNA. Putative transcriptional termination sites were found approximately 220 bases (b) downstream from the end of the 28S coding region. Comparison of the 2.3-kb fragments with two longer (3.1 kb) fragments showed that the major difference in length resulted from variation in the number of short (89 b) repeats located 3′ to the putative terminator. Repeat units within a single nucleolus organizer region (NOR) appeared relatively homogeneous and genetic analysis found variants to be stably inherited. A comparison of the number of spacer-length variants with the number of NORs found that the number of length variants per individual was always less than the number of NORs. Examination of spacer variants in five populations showed that populations with more NORs had more spacer variants, indicating that variants are present at different rDNA sites on nonhomologous chromosomes.Key words: ribosomal DNA, lake trout, intergenic spacer, repetitive DNA.

The molecular characterization of the genome of Muraena helena L. I. Isolation and hybridization of two MboI-restricted DNA fractions

Genome ◽  
1995 ◽  
Vol 38 (4) ◽  
pp. 809-813 ◽  
Author(s):  
G. Pichiri ◽  
M. Nieddu ◽  
R. Mezzanotte ◽  
P. P. Coni ◽  
S. Salvadori ◽  
...  
Keyword(s):  
Repetitive Dna ◽  
Organizer Region ◽  
Nucleolar Organizer Region ◽  
Electrophoretic Pattern ◽  
Nucleolar Organizer ◽  
Fish Chromosomes ◽  
Highly Repetitive Dna ◽  
Total Dna

To investigate the genome of the anguilliform fish Muraena helena at the molecular level we characterized total DNA by agarose gel electrophoresis after cleavage with AluI, HaeIII, MboI, and DdeI restriction endonucleases. Subsequently, we isolated the DNA from two specific electrophoretic fractions to be used as probes for Southern and in situ hybridization experiments. One such fraction showed an electrophoretic pattern typical of highly repetitive DNA localized in the centromeres of many chromosomes. The other fraction was shown to be located in the nucleolar organizer region, partially coincident with 45S rDNA, and to be composed of highly repetitive sequences.Key words: fish chromosomes, rDNA, highly repetitive DNA.

Variation of the intergenic spacer region of ribosomal DNA in cultivated and wild rice species

Genome ◽  
1990 ◽  
Vol 33 (2) ◽  
pp. 209-218 ◽  
Author(s):  
Y. Sano ◽  
R. Sano
Keyword(s):  
Ribosomal Dna ◽  
Intergenic Spacer ◽  
Length Variation ◽  
Cultivated Rice ◽  
Spacer Length ◽  
Intergenic Spacer Region ◽  
Wild Rice Species ◽  
Cultivated Species ◽  
Restriction Enzyme Maps ◽  
Spacer Length Variants

Spacer-length variation in ribosomal DNA (rDNA) was surveyed in two cultivated rice species and their wild relatives. Among 243 accessions observed, 18 different spacer-length variants were detected. Length heterogeneity was found within and among species as well as within individuals. Conventional genetic analysis revealed that two spacer-length variants were located at two unlinked loci. Restriction enzyme maps showed that length heterogeneity resulted from repetition of short repeated sequences in the intergenic spacer region in the Asian cultivar and its progenitor; however, the spacer region greatly differed from those of reproductively isolated taxa with respect to the length and the sequence. Furthermore, the Asian cultivated species and its progenitor were highly polymorphic for rDNA spacer-length variation and they were differentiated in frequencies of spacer-length variants as well as varietal groups within the cultivated species. Asian cultivars tended to carry homogeneous repeats of rDNA compared with their progenitor, suggesting different forms of homogenization occurring in Asian cultivars.Key words: ribosomal DNA, intergenic spacer, polymorphism, inheritance, Oryza.

Ribosomal DNA variations in wild and cultivated rubber tree (Hevea brasiliensis)

Genome ◽  
1993 ◽  
Vol 36 (6) ◽  
pp. 1049-1057 ◽  
Author(s):  
Pascale Besse ◽  
Marc Seguin ◽  
Patricia Lebrun ◽  
Claire Lanaud
Keyword(s):  
Ribosomal Dna ◽  
Hevea Brasiliensis ◽  
Geographical Origin ◽  
Rubber Tree ◽  
Intergenic Spacer ◽  
Type I ◽  
Spacer Length ◽  
High Level ◽  
Dna Variations ◽  
Spacer Length Variants

Ribosomal DNA variations were surveyed to assess the genetic variability among Hevea brasiliensis genetic resources. One hundred and sixty-eight individuals, including 73 cultivated Wickham clones and 95 wild clones from a prospection, were analyzed. Restriction mapping of rDNA units showed that RFLP variations are the result of both length and site (EcoRI) variations in the intergenic spacer (IGS). These variations can be revealed between as well as within individuals. A total of 12 spacer length variants is scored in the whole population, as well as two different ribosomal units (refered as type I and type II), defined by the presence or absence of an EcoRI site. Particular associations between spacer length variants and unit types can be revealed, leading to complex RFLP patterns. Cultivated clones appear to be less variable than prospections but show, however, a relatively high level of variability despite their narrow genetic base. Furthermore, IGS variations allowed a structuring within wild clones to be drawn, based mainly on their geographical origin. Some interesting discrepancies with previous work on isozyme variations are discussed and show the interest of surveying different genetic markers for diversity studies.Key words: Hevea brasiliensis, RFLP, rDNA, genetic diversity.

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