The ribosomal RNA genes in synthetic tetraploids of wheat

Fränkel, O. H.; Gerlach, W. L.; Peacock, W. J.

doi:10.1007/bf00249154

Cited by 16 publications

(8 citation statements)

References 18 publications

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“…3). Similar results were reported by Frankel et al (1988) in a synthetic tetraploid (AABB) wheat using the 18s + 26s rDNA probe. The in situ hybridization pattern of the 18s + 26s rDNA probe in this study supports the findings of Friebe et al (1990), Miller et al (1983), which indicated that only four chromosomes (two pairs) in T. monococcum carry 18s + 26s rDNA and the findings of Miller et al (1980) that these are located next to the satellites in this species.…”

Section: In Situ Hybridizationsupporting

confidence: 91%

“…In the tetraploid wheat species T. turgidum, only chromosomes 1B and 6B showed hybridization (Appels and Dvoiak 1982;Armstrong et al 1991). Frankel et al (1988), using a synthetic tetraploid (AABB) and a 'H-labelled 18s + 26s rRNA probe, demonstrated that chromosome 1B labelled in situ more than chromosome 6B and one pair of chromosomes also labelled more than another pair in the A genome. Miller et al (1 983) demonstrated that a labelled 18s + 26s rRNA probe hybridized in situ to a pair of A genome chromosomes in T. urartu.…”

Section: Introductionmentioning

confidence: 95%

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Genetic and cytogenetic analyses of the A genome of Triticum monococcum. VIII. Localization of rDNAs and characterization of 5S rRNA genes

Kim¹,

Kuspira²,

Armstrong³

et al. 1993

Genome

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In situ hybridization with [3H]dCTP labelled pScT7 (5S rDNA) and pTa80 (18S + 26S rDNA) indicated that both hybridized to the terminal regions of two pairs of chromosomes in Triticum monococcum. When the hybridization was performed with a mixture of both probes, only two pairs of chromosome arms were labelled, which suggested that the loci of both genes were located in juxtaposition to one another. Both probes labelled one pair of sites more heavily than the other. Southern analysis of 5S with BamHI-digested DNA from 12 accessions of T. monococcum (including T. urartu) produced two superimposed ladders of approximate sizes of 500 and 330 bp, which differ from T. aestivum in which 500- and 420-bp ladders were found. The 500-bp ladder is derived from chromosome 5A (5SDna-A2) and the 330-bp ladder from chromosome 1A (5SDna-A1). The recognition site for SstI was present in the long spacer region but absent in the short spacer as in T. aestivum; however, unlike T. aestivum, there were HaeIII (GGCC) and HindIII (AAGCTT) recognition sites in the short spacer region. The TaqI recognition sites (TCGA) in the long and short spacer regions are probably more highly methylated in T. monococcum than in T. aestivum. The results have implications regarding the evolutionary changes that occurred in the A genome of the hexaploid compared with the diploid.

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Section: In Situ Hybridizationsupporting

confidence: 91%

Section: Introductionmentioning

confidence: 95%

Genetic and cytogenetic analyses of the A genome of Triticum monococcum. VIII. Localization of rDNAs and characterization of 5S rRNA genes

Kim¹,

Kuspira²,

Armstrong³

et al. 1993

Genome

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“…On the other hand synthetic AABB tetraploids (Frankel et al 1987) show no significant reduction of the A genome rDNA after 10 generations and, in addition, the A chromosome rDNA is transcriptionally active.…”

Section: Discussionmentioning

confidence: 92%

Variation in the restriction fragments of 18S–26S rRNA loci in South American Elymus (Triticeae)

Dubcovsky¹,

Lewis²,

Hopp³

1992

Genome

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The repeat units of the 18S–5.8S–26S ribosomal genes (rDNA) of 15 South American and 6 Asiatic and North American species of Elymus were shown to vary between 8.7 and 11.3 kb among species. Interspecific variation in the EcoRI and BamHI cleavage sites was observed. BamHI restriction sites were present in the subrepeats in the intergenic spacers in rDNA from diploid Hordeum (H genome) and absent in the diploid Pseudoroegneria (S genome) and in nearly all the tetraploid species of Elymus (SH genomes). Tetraploid Elymus species have only two pairs of chromosomes with secondary constrictions similar to those found in Pseudoroegneria and a maximum of two different repeat unit length classes. These results suggest that the rDNA in the H genome was lost during the evolution of the tetraploid Elymus. However, the additional H genome present in the hexaploid Elymus with genome formula SSHHH′H′ still show active ribosomal genes. Nucleolar organizer activity was also observed in rDNA from both the S and H genomes in artificial SS × HH amphiploids, suggesting no complete nucleolar dominance (amphiplasty) between the S and H genomes.Key words: Elymus, ribosomal genes, RFLP, nucleolus.

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“…The major 45S rDNA loci in diploid wheat are distributed on the 1A, 5A, 1B, 6B, and 5D chromosomes, and some of these loci, also called the nucleolus organizing region (NOR), became minor loci in tetraploid and hexaploid wheat during the course of evolution (Flavell and O'Dell, 1979;Appels et al, 1980;Miller et al, 1983;Frankel et al, 1987). The activities of NORs are related to the size of the intergenic regulatory region and the status of cytosine methylation in wheat (Sardana et al, 1993;Dubcovsky and Dvorák, 1995;Neves et al, 1995;Houchins et al, 1997;Akhunov et al, 2001Silva et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

Asymmetric Epigenetic Modification and Elimination of rDNA Sequences by Polyploidization in Wheat

Guo

Han

2014

Plant Cell

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ORCID ID: 0000-0001- 8393-3575 (F.H.) rRNA genes consist of long tandem repeats clustered on chromosomes, and their products are important functional components of the ribosome. In common wheat (Triticum aestivum), rDNA loci from the A and D genomes were largely lost during the evolutionary process. This biased DNA elimination may be related to asymmetric transcription and epigenetic modifications caused by the polyploid formation. Here, we observed both sets of parental nucleolus organizing regions (NORs) were expressed after hybridization, but asymmetric silencing of one parental NOR was immediately induced by chromosome doubling, and reversing the ploidy status could not reactivate silenced NORs. Furthermore, increased CHG and CHH DNA methylation on promoters was accompanied by asymmetric silencing of NORs. Enrichment of H3K27me3 and H3K9me2 modifications was also observed to be a direct response to increased DNA methylation and transcriptional inactivation of NOR loci. Both A and D genome NOR loci with these modifications started to disappear in the S4 generation and were completely eliminated by the S7 generation in synthetic tetraploid wheat. Our results indicated that asymmetric epigenetic modification and elimination of rDNA sequences between different donor genomes may lead to stable allopolyploid wheat with increased differentiation and diversity.

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The ribosomal RNA genes in synthetic tetraploids of wheat

Cited by 16 publications

References 18 publications

Genetic and cytogenetic analyses of the A genome of Triticum monococcum. VIII. Localization of rDNAs and characterization of 5S rRNA genes

Genetic and cytogenetic analyses of the A genome of Triticum monococcum. VIII. Localization of rDNAs and characterization of 5S rRNA genes

Variation in the restriction fragments of 18S–26S rRNA loci in South American Elymus (Triticeae)

Asymmetric Epigenetic Modification and Elimination of rDNA Sequences by Polyploidization in Wheat

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