Polyploidy in plants an introduction Polyploidy in plants an introduction My credentials selection of Washington University for Ph D work Walter Lewis and International Conference on Polyploidy Biological Relevance May 1979 Polyploidy in plants an introduction selected to work with Barbara Schaal Peter Raven expert on polyploid evolution especially in California taxa Polyploidy in plants an introduction lab mates with Jeff Doyle Ph D on polyploid Claytonia spring beauty at Indiana with Charlie Heiser but doing post doc with Walter Lewis and Roger Beachy on polyploidy in Glycine soybean Polyploidy in plants an introduction Jeff Doyle was the Ph D advisor of Eve Emshwiller at Cornell Polyploidy in plants an introduction while at Washington University Jeff Palmer then a postdoc at Stanford now at Indiana gave a talk on molecular phylogenetics presented DNA evidence to solve portions of U s triangle on Brassica polyploid evolution provided Washington U with probes to do molecular phylogenetic work Polyploidy in plants an introduction I went onto Davis for a postdoc with Les Gottlieb to look at DNA based relationships of diploids and polyploids in Clarkia for various reasons other issues in Clarkia became more important Cody Williams is now finishing the original story first begun in Davis and earlier by Raven C purpurea n 26 Polyploidy in plants an introduction in 1984 three people vied for the first two plant molecular systematics positions in the world at Madison and Ithaca myself Jeff Doyle and Jonathan Wendel Polyploidy in plants an introduction Jonathan Wendel now at Ames switched over into more evolutionary genomics questions e g Gossypium polyploidy Polyploidy in plants an introduction Tom Osborn and Keming Song UW Agronomy sat in on my Bot 563 to learn how to phylogenetically analyze their Brassica data Polyploidy in plants an introduction shortly thereafter David Spooner rotated in my lab for one year to learn how to do DNA phylogenetic analysis on Solanum sect Petota he was kind enough to include me as author on two papers dealing with polyploid evolution in this group more on that story later Polyploidy in plants an introduction David Baum joined my lab in 1990 as postdoc to do phylogenetic analysis of Epilobium and relatives to address chromosome number and polyploid evolution Polyploidy in plants an introduction Chris Pires my graduate student and now at U Missouri does postdocs with Soltis and Soltis on Tragopogon and later with Osborn on Brassica Polyploidy a history Polyploids plants containing more than the normal number two sets of chromosomes Aneuploids plants containing fewer or more chromosomes from the basic x or multiples of x number of chromosomes if x 6 then a diploid would have 2n 12 chromosomes Polyploids would have 2x 12 or 2n 24 for example tetraploid 4 sets Aneuploids would have deviated from x 6 to have 2n 10 2n 8 or 2n 14 for example Polyploidy a history Hugo DeVries published Mutation Theory in 1901 polyploid mutants in Oenothera played an important role in his work Oenothera lamarckiana on book face Polyploidy a history selected this species in 1886 because appeared to be good candidate for saltational mutants did large scale greenhouse experiments to find mutants Polyploidy a history of many the gigas mutant is important here as it turned out to be a spontaneously derived tetraploid 2n 14 is typical for Oenothera Polyploidy a history DeVries and Gates had long argument over the nature of gigas in terms of impact on everything from increase cell size to more robust plant vigor Polyploidy a history Eduard Strasburger 1844 1912 founder of modern cytology first coins the term polyploid Polyploidy a history Winkler 1916 earliest study of polyploidy by forming chimaeras between different species of Solanum Tissue of the anther wall showing high polyploid cells side by side with diploid cells from Briggs Walters 1997 Polyploidy a history O Winge 1917 first classic paper on polyploid distinguishes two types of polyploids autopolyploids derived within a single individual allopolyploids polyploidy succeeding hybridization Kihara and Ono 1926 actually coin the terms autopolyploidy and allopolyploidy Polyploidy a history autopolyploidy allopolyploidy Polyploidy a history Clausen Goodsend 1925 form hexaploid tobacco Nicotiana glutinosa 2n 24 diploid 1x N tabacum X 2n 48 tetraploid 2x 2n 72 hexaploid 3x Polyploidy a history Karpechenko 1925 derives radish X cabbage polyploid hybrid Raphanobrassica Georgi Karpechenko 1899 1941 Polyploidy a history A viable hybrid progeny individual was produced from seed However this hybrid was functionally sterile because the 9 chromosomes from the cabbage parent were different enough from the radish chromosomes that pairs did not synapse and segregate normally Eventually one part of the hybrid plant produced some seeds On planting these seeds produced fertile individuals with 36 chromosomes They had apparently been derived from spontaneous accidental chromosome doubling to 2n1 2n2 in one region of the sterile hybrid presumably in tissue that eventually became germinal and underwent meiosis Unfortunately for Karpechenko his allopolyploid had the roots of a cabbage and the leaves of a radish Karpechenko in the original cabbage patch Polyploidy formation doubled chromosomes in somatic cells mitosis or unreduced gametes meiosis occur infrequently but do occur experimentally this can be done by the addition of the alkaloid colchicine Polyploidy formation Colchicum autumnale meadow saffron from Briggs Walters 1997 Polyploidy reproductive isolation Once formed allopolyploids are reproductively isolated from other species of other ploidy levels Polyploidy reproductive isolation Once formed allopolyploids are reproductively isolated from other species of other ploidy levels from Briggs Walters 1997 Meiosis in a triploid hybrid Note mixtures of bivalents black and univalents white at metaphase I of meiosis Polyploidy types autopolyploidy allopolyploidy Polyploidy types Ramsey Schemske 2002 Polyploids are defined either by mode of origin MO or by cytological criteria CC MO autopolyploids arise within single populations or between ecotypes of a single species whereas allopolyploids are derived from interspecific hybrids Autopolyploids have only homologous chromosomes allopolyploids have two or more sets of homeologous chromosomes CC allopolyploids are expected to display bivalent pairing lack of allosyndesis and disomic inheritance while
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