Ribosomal RNA genes in plants: variability in copy number and in the intergenic spacer

ABSTRACT We have compared the restriction patterns and copy numbers of ribosomal RNA genes (rDNA) between and within individuals of Vicia faba. While the Eco RI blot-hybridization patterns changed only after one to two generations, copy number changes were found among different tissues of the same plant. Copy number differences among individuals in the population were as great as 95-fold, whereas as much as a 12-fold variation was seen among tissues of the same plant. Among individual F1 progeny from genetic crosses, nearly an 8-fold variation was seen, and among individuals of the F2 generation a spread of 22-fold was measured. Among individual siblings of self-pollinated parents, up to 7-fold variation was observed. However, changes in copy number did not necessarily indicate changes in rDNA Eco RI blot-hybridization pattern, and vice versa. Furthermore, nearest neighbor analysis of R-loop experiments showed that the arrangement of members of the "nontranscribed" spacer (NTS) size classes along the chromosome was not random, but some clustering was indicated. The data are consistent with the hypothesis that sister chromatid exchange in somatic cells of V. faba is the primary mechanism for altering the rDNA copy number as well as causing the extreme variation observed in the NTS. Variation among individuals in rDNA blot-hybridization pattern was also observed for Vicia villosa, Vicia dasycarpa, Vicia benghalensis and Vicia pannonica.

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Dnase I Hypersensitive Sites within the Intergenic Spacer of Ribosomal RNA Genes in Reconstructed Barley Karyotypes

Biotechnology & Biotechnological Equipment ◽

10.1080/13102818.2009.10817608 ◽

2009 ◽

Vol 23 (1) ◽

pp. 1039-1043 ◽

Cited By ~ 2

Author(s):

A.D. Dimitrova ◽

E.D. Ananiev ◽

K.I. Gecheff

Keyword(s):

Ribosomal Rna ◽

Intergenic Spacer ◽

Dnase I ◽

Ribosomal Rna Genes ◽

Dnase I Hypersensitive Sites ◽

Hypersensitive Sites ◽

Rna Genes

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Chromosomal localization and copy number of 18s + 28S ribosomal RNA genes in evolutionarily diverse mosquitoes (Diptera, Culicidae)

Hereditas ◽

10.1111/j.1601-5223.1990.tb00094.x ◽

2008 ◽

Vol 113 (3) ◽

pp. 277-289 ◽

Cited By ~ 43

Author(s):

A. KUMAR ◽

KARAMJIT S. RAI

Keyword(s):

Ribosomal Rna ◽

Copy Number ◽

Chromosomal Localization ◽

Ribosomal Rna Genes ◽

Rna Genes

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Comparison of nuclear ribosomal RNA genes among Solanum species and other Solanaceae

Genome ◽

10.1139/g94-038 ◽

1994 ◽

Vol 37 (2) ◽

pp. 271-279 ◽

Cited By ~ 24

Author(s):

N. Borisjuk ◽

L. Borisjuk ◽

G. Petjuch ◽

V. Hemleben

Keyword(s):

Ribosomal Rna ◽

Ribosomal Dna ◽

New World ◽

Intergenic Spacer ◽

Solanum Species ◽

Ribosomal Rna Genes ◽

Nucleotide Sequence Analysis ◽

World Species ◽

Old World ◽

Rna Genes

The organization of the nuclear-encoded 18S, 5.8S, and 25S ribosomal RNA genes (ribosomal DNA; rDNA) of 21 New World species from different sections of the genus Solanum, of two Old World Solanum species, and of representatives of other Solanaceae (Nicotiana, Atropa, Datura, Physalis, and Capsicum) was analyzed by restriction enzyme mapping using different rDNA specific hybridization probes. All Solanum species investigated exhibited rDNA repeats between 8.7 and 9.3 kb in length; the only exception was S. neorossii with a repeat length of 10.3 kb. Sequence heterogeneity was observed mostly in the intergenic spacer (IGS) region. Restriction sites for EcoRI and DraI in the spacer sequences were found to be characteristic for the New World species of the genus Solanum and for Lycopersicon esculentum. An additional XbaI site was detected in the spacer region of two nontuber-bearing species, S. brevidens and S. etuberosum (subsection Estolonifera Hawkes; series Etuberosa), as well as in the primitive tuber-bearing species of the series Pinnatisecta and Polyadenia (subsection Potatoe G.Don), thus demonstrating that these Mexican species are separated from the other tuber-bearing species but are closely linked to the nontuber-bearing Estolonifera group. Two EcoRI sites mapped at the 3′end of the 25S rRNA coding region seem to be characteristic for members of the Solanaceae; the first EcoRI site is apparently methylated in approximately 50% of the rDNA repeats. Southern hybridization with an IGS fragment of Solanum tuberosum as hybridization probe and nucleotide sequence analysis of the phylogenetically informative 3′ end of the 25S rDNA support the assumption that the New World species of the genus Solanum are closely related to Lycopersicon (tomato) in contrast with other Solanaceae investigated, Nicotiana, Atropa, Datura, Physalis, and Capsicum. Moreover, the New World potatoes and tomato appear to be more closely related to each other than potatoes and the Old World species Solanum nigrum and Solanum dulcamara.Key words: ribosomal DNA, intergenic spacer, methylation, evolutionary relationship, phylogeny.

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