The Geraniaceae genomes project: Accelerated and coordinated evolution across the three plant genomes

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PI: Robert K. Jansen (University of Texas at Austin)Co-PIs: Jeffrey P. Mower (University of Nebraska)and Jeffrey D. Palmer (Indiana University)Senior Scientist: Tracey A. Ruhlman (University of Texas at Austin)Plant cells contain genomes in three distinct compartments, the mitochondrion, nucleus and plastid. The mitochondrial and plastid genomes originated by incorporation of an earlier bacterial cell into another. Over time, thousands of genes transferred among these genomes and now there is extensive communication among the compartments. This interaction has resulted in considerable conservation and stability of the genomes across the evolutionary tree of plants. The flowering plant family Geraniaceae, which includes Geranium and other common plants, represents a novel exception to this high level of conservation because both mitochondrial and plastid genomes have experienced remarkably accelerated rates of change in both gene content and order and rates of nucleotide substitutions. The cause of these accelerated rates is unknown, but may be directed by genes encoded in the nucleus. This project investigates the basis for this accelerated evolution with the aim of understanding how genomes within a single cell can influence one another and co-evolve over time. The project will sequence the DNA in mitochondrial genomes and will sequence the genes expressed in the nucleus and mitochondria of 16 members of the Geraniaceae and two related families. These data will be compared to plastid data for the same species to elucidate the mechanisms of inter-compartmental crosstalk and co-evolution in plant cells. The goals of this project are to determine the extent of genomic upheaval in the mitochondrial and plastid genomes of the Geraniaceae and to identify the correlated changes in the nuclear genome that have driven this instability. The results are expected to improve significantly our understanding of the mechanisms of how genes are exchanged across different compartments within all plant cells. The topic of genome evolution within cells is ideal for teaching students about how genomes evolved, interact and contribute to plant growth and development. The project will work with high school science students by offering summer research internships at each institution. For teacher training, workshops will be offered each year and specific teacher training modules will be developed in cooperation with public service groups, such as the Texas Natural Science Center and the Wonderlab Museum of Science in Bloomington, IN. The genomic resources generated by this project will be important for further genetic work with this horticulturally valuable plant family, which is estimated to generate $4 billion in sales annually on a worldwide basis. Ultimately, identifying the sources of rapid evolution in the Geraniaceae could provide genomic tools for understanding and potentially manipulating organelle genomes in other crop plants. These resources will be made available to the scientific community and the public through the creation of a project website (accessible via http://www.biosci.utexas.edu/ib/faculty/jansen.htm) and by depositing the data in long-term sequence databases at GenBank.