The Molecular Basis of Variation Affecting Gene Expression: Evidence from Studies on the Ribosmal RNA Gene Loci of Wheat

  • R. B. Flavell
  • R. Sardana
  • S. Jackson
  • M. O’Dell
Part of the Stadler Genetics Symposia Series book series (SGSS)


A question relevant to an understanding of plant breeding is “What is the molecular basis of allelic variation affecting gene expression?”. The importance of this question is elevated if one accepts the perhaps biased belief that much of the important variation that plant breeders exploit is concerned with variation in the amounts of gene products in time and space during plant development. Many other relevant questions emerge when one wonders about variation in gene expression. For example, does a gene adopt a different structure when it is active compared with when it is silent? How does a plant turn a gene off and on? What kinds of mutations cause a gene to be more or less active.


Cytosine Methylation rDNA Locus Hypersensitive Site CCGG Site Unmethylated Cytosine 


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  1. Barker, R.F., Harberd, N.P., Jarvis, M.G., and Flavell, R.B., 1988, Structure and Evolution of the intergenic region in a ribosomal DNA repeat unit of wheat, J. Mol. Biol., 201: 1–17.PubMedCrossRefGoogle Scholar
  2. Bell, S.P., Learned, R.M., Jantzen, H-M., and Tjian, R., 1988, Functional co-operativity between transcription factors UBA-1 and SL1 mediates human ribosomal RNA synthesis, Science, 241: 1192–1197.PubMedCrossRefGoogle Scholar
  3. Clos, J., Buttgereit, D., and Grummt, I., 1986, A purified transcription factor (TIF 1B) binds to essential sequences of the mouse rDNA promoter, Proc. Nat. Acad. Sci. (USA), 83: 604–608.CrossRefGoogle Scholar
  4. Coen, E.S., Carpenter, R., and Martin, C., 1986, Transposable elements generate novel spatial patterns of gene expression in Antirrhinum majus, Cell, 47: 285–296.PubMedCrossRefGoogle Scholar
  5. Dewinter, R.F.J., and Moss, T., 1987, A complex array of sequences enhances ribosomal transcription in Xenopus laevis, J. Mol. Biol, 196: 813–828.CrossRefGoogle Scholar
  6. Flavell, R.B., 1986, The structure and control of expression of ribosomal RNA genes, Oxford Surveys of Plant Molecular and Cell Biology, 3: 251–274.Google Scholar
  7. Flavell, R.B., 1989, Variation in structure and expression of ribosomal DNA loci in wheat, Genome, in press.Google Scholar
  8. Flavell, R.B., O’Dell, M., and Thompson, W.F., 1988, Regulation of cytosine methylation in ribosomal DNA and nucleolus organiser expression in wheat, J. Mol. Biol., 204: 523–534.PubMedCrossRefGoogle Scholar
  9. Jessop, C.M., and Subrahmanyan, N.C., 1984, Nucleolar number variation in Hordeum species; their haploids and interspecific hybrids, Genetica, 64: 93–100.CrossRefGoogle Scholar
  10. Jones, M.H., Learned, R.M., and Tjian, R.T., 1988, Analysis of clustered point mutations in the human ribosomal RNA gene promoter by transient expression in vivo, Proc. Nat. Acad. Sci (USA), 85: 669–673.CrossRefGoogle Scholar
  11. Learned, R.M., Learned, T.K., Haltiner, M.M., and Tijian, R.T., 1986, Human rRNA transcription is modulated by the coordinate binding of two factors to an upstream control element, Cell, 45: 847–857.PubMedCrossRefGoogle Scholar
  12. Martini, G., and Flavell, R.B., 1985, The control of nucleolus volume in wheat; a genetic study at three development stages, Heredity, 54: 111–120.CrossRefGoogle Scholar
  13. Martini, G., O’Dell, M., and Flavell R.B., 1982, Partial inactivation of wheat nucleolar organisers by the nucleolus organiser chromosomes from Aegilops umbellulata, Chromosoma, 84: 687–700.CrossRefGoogle Scholar
  14. Miller, K.G., Tower, J., and Sollner Webb, B., 1985, A complex control region of the mouse rRNA gene directs accurate initiation by RNA polymerase I, Mol. and Cell. Biol, 5: 554–562.Google Scholar
  15. Razin, A., and Riggs, A.D., 1980, DNA methylation and gene function, Science, 210: 604–610.PubMedCrossRefGoogle Scholar
  16. Reeder, R.H., 1984, Enhancers and ribosomal gene spacers, Cell, 38: 349–351.PubMedCrossRefGoogle Scholar
  17. Sollner Webb, B., Wilkinson, J., Roan, J., and Reeder, R., 1983, Nested control regions promote Xenopus rRNA synthesis by RNA polymerase I, Cell, 35: 199–206.CrossRefGoogle Scholar
  18. Thompson, W.F., an Flavell, R.B., 1988, DNase I sensitivity of ribosomal RNA genes in chromatin and nucleolar dominance in wheat, J. Mol. Bio., 204: 535–548.CrossRefGoogle Scholar
  19. Wallace, H., and Langridge, W.H.R., 1971, Differential amphiplasty and the control of ribosomal RNA synthesis, Heredity, 27: 113.CrossRefGoogle Scholar
  20. Yeh, B.P., and Peloquin, S.J., 1965, The nucleolus-associated chromosome of Solanum species and hybrids, Am. J. Bot, 52: 626.CrossRefGoogle Scholar

Copyright information

© Plenum Press, New York 1990

Authors and Affiliations

  • R. B. Flavell
    • 2
  • R. Sardana
    • 1
  • S. Jackson
    • 1
  • M. O’Dell
    • 1
  1. 1.Cambridge LaboratoryAFRC Institute of Plant Science ResearchTrumpington, CambridgeUK
  2. 2.John Innes Institute and AFRC Institute of Plant Science ResearchNorwich, NorfolkUK

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