Advertisement

Protoplasma

, Volume 232, Issue 1–2, pp 55–59 | Cite as

Relationships between transcription, silver staining, and chromatin organization of nucleolar organizers in Secale cereale

  • Ana D. Caperta
  • Nuno Neves
  • Wanda Viegas
  • Craig S. Pikaard
  • Sasha Preuss
Article

Summary.

The nucleolar organizer regions (NORs) are composed of hundreds of rRNA genes, typically spanning several megabases. Cytologically, NORs include regions that are highly condensed and regions that are decondensed, the latter corresponding to regions at which associated proteins stain intensively with silver (Ag-NORs) and where active rRNA gene transcription is thought to occur. To test the relationship between rRNA gene activity, NOR silver staining, and rDNA (genes coding for rRNA) chromatin condensation, we used the DNA methyl-transferase inhibitor 5-azacytidine to evaluate the correlation between the epigenetic regulation of rRNA genes and NOR silver staining in the plant Secale cereale. Following 5-azacytidine treatment, we observed an increase in rRNA gene transcription as well as a reduction in the number of cells showing a significant difference in the size of the silver-stained domains in the two NORs. These transcriptional changes occurred concomitantly with an increase in nuclear and nucleolar size and were associated with the reallocation of most of the rDNA from perinucleolar heterochromatin into the nucleolus. Collectively, these results suggest that rRNA gene transcription, silver staining, and NOR decondensation are interrelated in S. cereale.

Keywords: Nucleolar organizer region; Transcription; Silver staining; 5-Azacytidine; Secale cereale

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Abranches, R, Beven, AF, Aragón-Alcaide, L, Shaw, PJ 1998Transcription sites are not correlated with chromosome territories in wheat nucleiJ Cell Sci143512Google Scholar
  2. Caperta, A, Neves, N, Morais-Cecílio, L, Malhó, R, Viegas, W 2002Genome restructuring in rye affects the expression, organization and disposition of homologous rDNA lociJ Cell Sci11528392846PubMedGoogle Scholar
  3. Castilho, A, Neves, N, Rufini-Castiglione, M, Viegas, W, Heslop-Harrison, JS 19995-Methylcytosine distribution and genome organization in triticale before and after treatment with 5-azacytidineJ Cell Sci11243974404PubMedGoogle Scholar
  4. Chen, ZJ, Comai, L, Pikaard, CS 1998Gene dosage and stochastic effects determine the severity and direction of uniparental ribosomal RNA gene silencing (nucleolar dominance) in Arabidopsis allopolyploidsProc Natl Acad Sci USA951489114896PubMedCrossRefGoogle Scholar
  5. Delgado, M, Morais-Cecílio, L, Neves, N, Jones, RN, Viegas, W 1995The influence of B chromosomes on rDNA organization in rye interphase nucleiChromosome Res3487491PubMedCrossRefGoogle Scholar
  6. Derenzini, M 2000The AgNORsMicron31117120PubMedCrossRefGoogle Scholar
  7. Dundr, M, Olson, MOJ 1998Partially processed pre-rRNA is preserved in association with processing components in nucleolus derived foci during mitosisMol Biol Cell924072422PubMedGoogle Scholar
  8. Dundr, M, Meier, UT, Lewis, N, Rekosh, D, Hammarskjöld, M-L, Olson, MOJ 1997A class of nonribosomal nucleolar components is located in chromosome periphery and in nucleolus-derived foci during anaphase and telophaseChromosoma105407417PubMedCrossRefGoogle Scholar
  9. Dundr, M, Misteli, T, Olson, MOJ 2000The dynamics of postmitotic reassembly of the nucleolusJ Cell Biol150433446PubMedCrossRefGoogle Scholar
  10. Gerlach, WL, Bedbrook, JR 1979Cloning and characterization of ribosomal RNA genes from wheat and barleyNucleic Acids Res718691885PubMedCrossRefGoogle Scholar
  11. Goodpasture, C, Bloom, SE 1975Visualization of nucleolar organizer regions in mammalian chromosomes using silver stainingChromosoma533750PubMedCrossRefGoogle Scholar
  12. Lawrence, RJ, Earley, K, Pontes, O, Silva, M, Chen, ZJ, Neves, N, Viegas, W, Pikaard, CS 2004A concerted DNA methylation/histone methylation switch regulates rRNA gene dosage control and nucleolar dominanceMol Cell13599609PubMedCrossRefGoogle Scholar
  13. Leitch, IJ, Heslop-Harrison, JS 1992Physical mapping of the 18s-58-26s rRNA genes in barley by in situ hybridizationGenome3510131018Google Scholar
  14. Mais, C, Wright, JE, Prieto, J-L, Raggett, SL, McStay, B 2005UBF-binding site arrays form pseudo-NORs and sequester the RNA polymerase I transcription machineryGenes Dev195064PubMedCrossRefGoogle Scholar
  15. McStay, B, Reeder, RH 1986A termination site for Xenopus RNA polymerase I also acts as an element of an adjacent promoterCell47913920PubMedCrossRefGoogle Scholar
  16. Moreno, FJ, Rodrigo, RM, Garcia-Herdugo, G 1990Ag-NOR proteins and rDNA transcription activity in plant cellsJ Histochem Cytochem3818791887PubMedGoogle Scholar
  17. Neves, N, Silva, M, Heslop-Harrison, JS, Viegas, W 1997Nucleolar dominance in triticales: control by unlinked genesChromosome Res5125131PubMedCrossRefGoogle Scholar
  18. Roussel, P, Andre, C, Comai, L, Hernandez-Verdun, D 1996The rDNA transcription machinery is assembled during mitosis in active NORs and absent in inactive NORsJ Cell Biol133235246PubMedCrossRefGoogle Scholar
  19. Schwarzacher, T, Heslop-Harrison, JS 2000Practical in situ hybridisationBios Scientific PublishersOxfordGoogle Scholar
  20. Shaw, P, Rawlins, D, Highett, M 1993Nuclear and nucleolar structure in plantsHeslop-Harrison, JSFlavell, RB eds. The chromosomeBios Scientific PublishersOxford161171Google Scholar
  21. Vieira, R, Queiroz, A, Morais, L, Barão, A, Mello-Sampayo, T, Viegas, W 19901R chromosome nucleolus organizer region activation by 5-azacytidine in wheat-rye hybridsGenome33707712Google Scholar

Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  • Ana D. Caperta
    • 1
    • 2
  • Nuno Neves
    • 1
    • 4
  • Wanda Viegas
    • 1
  • Craig S. Pikaard
    • 3
  • Sasha Preuss
    • 3
  1. 1.Centro Botânica Aplicada à Agricultura, Instituto Superior de AgronomiaTechnical University of LisbonLisboa
  2. 2.Departamento de Ciências Biológicas e NaturaisUniversidade Lusófona de Humanidades e TecnologiasLisboa
  3. 3.Biology DepartmentWashington UniversitySt. Louis
  4. 4.Secção Autónoma de Biotecnologia, Faculdade de Ciências e TecnologiaUniversidade Nova de LisboaCaparica

Personalised recommendations