Contributed as many data as the first author
Long-term genome diploidization in allopolyploid Nicotiana section Repandae (Solanaceae)
Article first published online: 1 JUL 2005
Volume 168, Issue 1, pages 241–252, October 2005
How to Cite
Clarkson, J. J., Lim, K. Y., Kovarik, A., Chase, M. W., Knapp, S. and Leitch, A. R. (2005), Long-term genome diploidization in allopolyploid Nicotiana section Repandae (Solanaceae). New Phytologist, 168: 241–252. doi: 10.1111/j.1469-8137.2005.01480.x
- Issue published online: 1 JUL 2005
- Article first published online: 1 JUL 2005
- Received: 27 January 2005 Accepted: 12 April 2005
- FISH (fluorescent in-situ hybridization);
- GISH (genomic in-situ hybridization);
- • Here, we analyze long-term evolution in Nicotiana allopolyploid section Repandae (the closest living diploids are N. sylvestris, the maternal parent, and N. obtusifolia, the paternal parent). We compare data with other more recently formed Nicotiana allopolyploids.
- • We investigated 35S and 5S nuclear ribosomal DNA (rDNA) chromosomal location and unit divergence. A molecular clock was applied to the Nicotiana phylogenetic tree to determine allopolyploid ages.
- • N. tabacum and species of Repandae were c. 0.2 and 4.5 Myr old, respectively. In all Repandae species, the numbers of both 35S and 5S rDNA loci were less than the sum of those of the diploid progenitors. Trees based on 5S rDNA spacer sequences indicated units of only the paternal parent.
- • In recent Nicotiana allopolyploids, the numbers of rDNA loci equal the sum of those of their progenitors. In the Repandae genomes, diploidization is associated with locus loss. Sequence analysis indicates that 35S and 5S units most closely resemble maternal and paternal progenitors, respectively. In Nicotiana, 4.5 Myr of allopolyploid evolution renders genomic in situ hybridization (GISH) unsuitable for the complete resolution of parental genomes.