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Plant of the Day

Explore the evolutionary significance of polyploidy in plants, from diploidization to paleopolyploidy, with a focus on unresolved questions and mechanisms that drive long-term success. Discover key studies and analyses shedding light on genome duplication events and their impact on speciation and extinction rates.

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Plant of the Day

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  1. Plant of the Day Cyperus esculentus - Cyperaceae Chufa (tigernut) 8,000 kg/ha, 720 kcal/sq m per month Top Crop for kcal productivity! One of the world’s worst weeds

  2. Big Questions • Is polyploidy an evolutionary dead-end? • If so, why are all plants the products of multiple polyploidization events? • How do polyploid genomes diploidize (i.e., what are the rules)?

  3. Paleopolyploidy • Ancient whole genome duplication • No different from neopolyploidy – except that it happened a long time ago • Track the historical contribution of polyploid speciation to evolution

  4. Polyploidy = Evolutionary noise (1970)‏ W. H. Wagner, Jr. “…polyploidy has contributed little to progressive evolution” (1971)‏ G. L. Stebbins

  5. Diploidization • Obscures evidence of paleopolyploidy • Return to a diploid genetic system • Restoration of full bivalent pairing • Gene and chromosome loss • Chromosomal rearrangements • Proceeds at different rates in different lineages

  6. Rosa Malus Cucumis Phaseolus Glycine Bruguiera Populus Linum Euphorbia Manihot Hevea Gossypium Citrus Thellungiella Arabidopsis Brassica Eucalyptus Vitis Rosids Eurosids 1 Eurosids 2

  7. Diploidization

  8. Methods for Identifying Paleopolyploidy • Fossils • Synteny relationships of duplicated genes – conserved gene order • Age estimates of duplicate genes

  9. Cell Size Increase • Consequence of genome size increase • 2 X increase in cell volume • 1.58 X increase in cell surface area 2n 4n

  10. Fossil Estimates Miocene Platanus Extant Platanus

  11. Fossil Estimates Miocene Platanus n > 7 – 9 70% angiosperms Extant Platanus

  12. Synteny Analyses Whole Genome Sequences

  13. Synteny Analyses Whole Genome Sequences

  14. Duplicate Gene Age Distributions No Paleopolyploidy % of Duplicate Pairs Ks (~ Time)‏

  15. Duplicate Gene Age Distributions Carthamus tinctorius % of Duplicate Pairs Ks (~ Time)‏

  16. Inferring Paleopolyploidy % of Duplicate Pairs Ks (~ Time)‏

  17. Previously Known Genome Duplications Barker et al., in prep

  18. Newly Recognized Genome Duplications Barker et al., in prep

  19. Newly Recognized Genome Duplications Li et al., 2015

  20. Newly Recognized Genome Duplications Infer 61 Independent Paleopolyploidizations 36 are newly observed All seed plants are ancient polyploids! Barker et al., in prep

  21. Significant increases in diversification rates in flowering plants • Half are associated with paleopolyploidy (p = 0.005)

  22. What about neo-polyploidy? Application of BISSE: binary-state speciation and extinction (likelihood method developed by Maddison et al. 2007) Polyploidy:  speciation,  extinction (I. Mayrose et al. 2011, Science) Extinction Speciation number of cases number of cases higher rate in diploids higher rate in diploids

  23. Resolution Polyploidy is most often an evolutionary dead end, but the expanded genomic potential of those polyploids that do persist drives longer term evolutionary success.

  24. Unanswered questions Do auto- and allopolyploids differ in their evolutionary success? What factors control the fate of duplicate genes? How long must a polyploid lineage persist before it transitions from a trajectory that favors extinction to one that favors diversification? What evolutionary genetic changes/processes underlie this transition?

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