Long-term genome diploidization in allopolyploid Nicotiana section Repandae (Solanaceae)

• 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 nuc...

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Bibliographic Details
Published in:The New phytologist 2005-10, Vol.168 (1), p.241-252
Main Authors: Clarkson, James J., Lim, K. Yoong, Kovarik, Ales, Chase, Mark W., Knapp, Sandra, Leitch, Andrew R.
Format: Article
Language:English
Subjects:
Allopolyploidy
Biological and medical sciences
Biological Evolution
Biological taxonomies
chromosome mapping
cytogenetics
diploidization
Diploidy
DNA, Plant
DNA, Ribosomal - genetics
Evolution
Evolutionary genetics
FISH (fluorescent in‐situ hybridization)
fluorescence in situ hybridization
Fundamental and applied biological sciences. Psychology
Genetic loci
genetic variation
genome
Genome, Plant
Genomes
Genomics
GISH (genomic in‐situ hybridization)
molecular evolution
molecular sequence data
Nicotiana
Nicotiana - genetics
nucleotide sequences
phylogenetics
Phylogeny
Plant cytology, morphology, systematics, chorology and evolution
plant genetics
plant taxonomy
Ploidies
Polyploidy
Repandae
Ribosomal DNA
sequence analysis
Solanaceae
Southern blotting
Species Specificity
Spermatophyta
Systematics (diagnosis, chromosome numbers)
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Summary:• 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.
ISSN:0028-646X
1469-8137
DOI:10.1111/j.1469-8137.2005.01480.x