Soltis_BU - A Double Dose of Genes-A New Look at an Old...

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1 A Double Dose of Genes-- A New Look at an Old Process or The Genetic and Genomic Consequences of Polyploidy Pamela S. Soltis Florida Museum of Natural History University of Florida Polyploidy DIPLOID - Nucleus contains two copies of each chromosome POLYPLOID - Nucleus contains three or more copies of each chromosome AUTOPOLYPLOID - formed from a single species ALLOPOLYPLOID - combines the genomes of more than one species John Celenza: See lecture from March 18
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2 Polyploidy DIPLOID - Nucleus contains two copies of each chromosome POLYPLOID - Nucleus contains three or more copies of each chromosome AUTOPOLYPLOID - formed from a single species ALLOPOLYPLOID - combines the genomes of more than one species Significance of Polyploidy • ~50% of all flowering plants are of polyploid origin (traditional estimate; stay tuned) • 95% of all ferns may be polyploid • 17 of the 18 world’s worst weeds are polyploid • Many major crops are polyploid – Wheat, corn, sugar cane, cotton, potato, coffee • Tremendous economic importance
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3 Extent of Polyploidy: Examples Taxon Chromosome Numbers Sedum 16, 24, 32, 38, 56, 64, 128 - 640 Saxifraga 10 - 200 Claytonia virginica 12 - 192 Ophioglossum 200 - 1260 Polyploidy: Traditional Views • Polyploidization events rare; a “plant thing” • Autopolyploids considered rare • Each polyploid species has had a single origin -Genetic uniformity across individuals of new polyploid -“Buffering effect” of multiple genomes-- mutation and recombination less effective at constructing new adaptive gene complexes • Polyploids as “evolutionary dead ends” W. H. Wagner G. L. Stebbins
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4 Arabidopsis Small genome (157 Mbp), but…. Two or three rounds of genome duplication (Vision et al., 2001; Bowers et al., 2003) John Celenza: Arabidopsis is a dicot; Oryza is rice and shows when monocots split from dicots about 170 million years ago Theoretical age distributions of pairs of duplicated genes From Blanc & Wolfe, 2004 John Celenza: The number of duplicated genes in a genome decreases the longer the time since the duplication event. New duplications cause a new peak.
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5 Genome-wide Duplication: Blanc and Wolf (2004) Genomics approach: characteristic signature of genome duplication-- peak in frequency distribution of duplicate gene pairs Duplicated gene pairs (%) K s (time) K (time) Many Genome-wide Duplications: Blanc and Wolf (2004) Evidence of genome duplications in many plants
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6 Basal Angiosperms as Ancient Polyploids 0 5 10 15 20 25 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.9 2 0 1 2 3 4 5 6 7 8 9 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2 Series1 0 5 10 15 20 25 30 35 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 2 2.1 Ks Freq 0 5 10 15 20 25 30 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2 Acorus -basal monocot poppy-basal eudicot water lily-basal angiosperm avocado-magnoliid Floral Genome Project: Cui et al. 2006 Genomics approach using ESTs • Revised estimate---closer to 100% • Are there any diploids?
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Soltis_BU - A Double Dose of Genes-A New Look at an Old...

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