Transcription activity of rRNA genes correlates with a tendency towards intergenomic homogenization in Nicotiana allotetraploids
Article first published online: 7 MAR 2007
Volume 174, Issue 3, pages 658–668, May 2007
How to Cite
Dadejová, M., Lim, K. Y., Soucková-Skalická, K., Matyášek, R., Grandbastien, M.-A., Leitch, A. and Kovařík, A. (2007), Transcription activity of rRNA genes correlates with a tendency towards intergenomic homogenization in Nicotiana allotetraploids. New Phytologist, 174: 658–668. doi: 10.1111/j.1469-8137.2007.02034.x
- Issue published online: 7 MAR 2007
- Article first published online: 7 MAR 2007
- Received: 7 December 2006 Accepted: 16 January 2007
- gene conversion;
- nucleolar dominance;
- rDNA silencing;
- ribosomal RNA
- • This paper establishes relationships between two aspects of ribosomal DNA (rDNA) biology: epigenetic silencing of rDNA loci; and homogenization leading to concerted evolution.
- • Here, we examined rDNA inheritance and expression patterns in three natural Nicotiana allopolyploids (closest living descendants of diploid parents are given), N. rustica (N. paniculata × N. undulata), N. tabacum (N. sylvestris × N. tomentosiformis) and N. arentsii (N. undulata × N. wigandioides), and synthetic F1 hybrids and allopolyploids.
- • The extent of interlocus rDNA homogenization decreased in the direction N. arentsii > N. tabacum > N. rustica. The persistence of parental rDNA units in one of the subgenomes was associated with their transcription inactivity and likely heterochromatization. Of synthetic hybrids and polyploids only N. paniculata × N. undulata showed strong uniparental transcriptional silencing of rDNA triggered already in F1.
- • Epigenetic patterns of expression established early in allopolyploid nucleus formation may render units susceptible or resistant to homogenization over longer time-frames. We propose that nucleolus-associated transcription leaves rDNA units vulnerable to homogenization, while epigenetically inactivated units, well-separated from the nucleolus, remain unconverted.