ArticleAnnals of botany2014
Incomplete sequence homogenization in 45S rDNA multigene families: intermixed IGS heterogeneity within the single NOR locus of the polyploid species Medicago arborea (Fabaceae).
Article in Annals of botany, 2014. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 10 papers.
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10 citing papers in PubMed, 13 citations in OpenAlex.
- Transcriptional Silencing of 35S rDNA inInternational journal of molecular sciences · 2024Article
- The Divergence of Chromosome Structures and 45S Ribosomal DNA Organization inPlants (Basel, Switzerland) · 2022Article
- The Ribosomal DNA Loci of the Ancient MonocotFrontiers in plant science · 2022Article
- InterstitialPlants (Basel, Switzerland) · 2021Article
- Inter- and intraspecific hypervariability in interstitial telomeric-like repeats (TTTAGGG)n in Anacyclus (Asteraceae).Annals of botany · 2018Article
- High and uneven levels of 45S rDNA site-number variation across wild populations of a diploid plant genus (Anacyclus, Asteraceae).PloS one · 2017Article
- Comparative genetic analysis of the 45S rDNA intergenic spacers from three Saccharum species.PloS one · 2017Article
- 45S rDNA external transcribed spacer organization reveals new phylogenetic relationships in Avena genus.PloS one · 2017Article
- Article
- Diversity and Inheritance of Intergenic Spacer Sequences of 45S Ribosomal DNA among Accessions of Brassica oleracea L. var. capitata.International journal of molecular sciences · 2015Article
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3 authors at 1 institution in 1 country.
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No grant is acknowledged in the PubMed record.
Abstract
BACKGROUND AND
aimsRibosomal sequences have become the classical example of the genomic homogenization of nuclear multigene families. Despite theoretical advantages and modelling predictions that support concerted evolution of the 45S rDNA, several reports have found intragenomic polymorphisms. However, the origins and causes of these rDNA polymorphisms are difficult to assess because seed plants show a wide range of 45S rDNA loci number variation, especially in polyploids. Medicago arborea is a tetraploid species that has a single 45S rDNA locus. This feature makes this species a suitable case study to assess the fate of ribosomal IGS homogenization in polyploid species showing nucleolus organizer region (NOR) reduction.
methodsThe intergenic spacer (IGS) region was amplified by long PCR and the fragments were cloned and sequenced by a primer-walking strategy. The physical mapping of the whole and partial IGS variants was assessed by fluorescent in situ hybridization (FISH) and fibre-FISH methods on mitotic chromosomes and extended DNA fibres, respectively. KEY
resultsTwo IGS fragments of 4·8 and 3·5 kb were obtained showing structural features of functional sequences. The shorter variant appears to be a truncated copy of the 4·8 kb fragment that lacks the duplication of the transcription initiation site region and the entire D region. The physical localization of the two IGS variants on metaphase chromosomes and extended DNA fibres using FISH corroborated their joint presence within the same locus. In addition, no spatial structure of the two variants was detected within the NOR.
conclusionsThe results suggest that full sequence homogenization is not operating within the NOR locus of M. arborea. The structure of the NOR locus reported here departs from the models of IGS heterogeneity present in plants and caution against assuming the widespread belief that intragenomic ribosomal heterogeneity is mainly due to sequence variation between paralogous loci.
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