Genome Evolution in Diploid and Polyploid Cotton

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PI: Jonathan F. Wendel (Iowa State University)Co-PIs: Adah Leshem-Ackerman (Iowa State University), Andrew H. Paterson (University of Georgia), Rod A. Wing (Arizona State University)The amount of DNA in plant genomes is highly variable among species, ranging by over three orders of magnitude. Relatively little is understood about the mechanisms by which this enormous variation in genome size arises, yet this feature of plant genomes undoubtedly has fundamental importance to many areas of biology and to crop productivity. To redress this gap in our knowledge, this project will address the tempo (e.g., regular vs. episodic bursts), directionality (with respect to genomic contraction or expansion), and absolute scale of genome size change, over time, in a model system involving diploid and tetraploid cotton species. The cotton genus is particularly well-suited to addressing this work, but the insights gleaned will extend to all plants. In addition, the work has relevance to the productivity and quality of one of the nation's leading crops. The study involves sequencing the same genomic regions from species that have genomes that vary twofold in size, as well as from a tetraploid species (with double the number of chromosomes) that originated from an ancient natural merger of these two smaller genomes. By sequencing large amounts of DNA, and by employing complementary molecular analyses of chromosomes, the research will reveal the relative roles of the various molecular and genetic mechanisms that are thought to underlie genome size change. The research also will lead to an improved understanding of the organization and architecture of plant genomes that have a great deal of repetitive DNA, and will provide unparalleled insight into the evolutionary processes responsible for genome evolution. During the course of this project, a spectrum of activities will be implemented that will enhance and broaden scientific training of students at all levels, including K-12 educators. Access to project outcomesSequence data will be deposited immediately in GenBank (http://www.ncbi.nlm.nih.gov/). The tools and resources developed through this project will be made available through the project web site, The Cotton Portal (http://gossypium.info).