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Molecular Ecology and Evolution

Chase, Mark W. [1], Clarkson, James J. [1], Leitch, Andrew R. [2], Lim, J.-Y. [2], Knapp, Sandra [3], Kovarik, Ales [4].

Genomic re-organization and phylogenetics of allotetraploids in Nicotiana (Solanaceae).

NICOTIANA is one of the largest genera of Solanaceae, and of its roughly 75 species 40% are allotetraploids. We have produced sequences from plastid and nuclear genes (ribosomal and low-copy protein coding) and used these to determine parentage of nearly all allotetraploid groups, some of which have radiated since their origin (e.g. sect. Suaveolentes with about 25 species distributed in Namibia and Australia). We have also established a molecular clock for the origins of the allotetraploids, so we have a time-scale for the changes in genomic organization. For recent allotetraploids, such as N. tabacum and N. rustica that are less than 200,000 years old, it is easy to clearly identify the parental chromosomes using genomic in-situ hybridization (GISH), and chromosome structure for 5S and 45S rDNA loci and various groups of repeats are exactly additive with respect to what one would predict from knowing that of their parents. In older allotetraploids, however, the effects of genomic diploidization are obvious. For example, in the four species of sect. Repandae that are 4.5 million years old, GISH no longer works well to identify parental contributions of chromosomes, and the number of ribosomal loci is altered to that typical of a diploid. In other groups of older allotetraploids, e. g. sect. Polydicleae, we observed similar changes.


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1 - Royal Botanic Gardens, Kew, Jodrell Laboratory, Richmond, Surrey, TW9 3AB, United Kingdom
2 - Queen Mary University of London, School of Biological Sciences, London, E1 4NS, United Kingdom
3 - Natural History Museum, Department of Botany, Cromwell Road, London, SW7 5BD, England
4 - Academy of Sciences of the Czech Republic, Institute of Biophysics, Brno, CZ-61265, Czech Republic

Keywords:
Nicotiana
GISH
allopolyploidy
Phylogenetics
Solanaceae.

Presentation Type: Oral Paper:Papers for Topics
Session: 26-7
Location: 350/Holt
Date: Monday, July 31st, 2006
Time: 3:30 PM
Abstract ID:89


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