Novel mechanisms of plant mitochondrial DNA repair

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The goal of this project is to provide fundamental knowledge of the energy conversion centers of plants that will allow scientists to engineer more energy efficient agricultural crops. The energy conversion centers or "powerhouses" of plant cells are called mitochondria, which are small membrane-bound compartments where the energy from carbon compounds is converted into a form that plant cells can use. Mitochondria have their own DNA, which is easily damaged and must be repaired to maintain efficient energy output. This project seeks to define the mechanism by which important gene sequences in mitochondrial DNA are repaired so that the efficient output of energy is maintained for plant growth. This project also seeks to provide training opportunities for graduate, undergraduate and high-school students, and to increase the diversity of students who are receiving research training.Plant mitochondrial genomes are notorious for their large and variable size, high rearrangement rates and low mutation rates. How coding sequences are highly conserved while the rest of the genome expands and rearranges is a mystery. Recent work suggests a model that the expansions and rearrangements are produced by error-prone repair mechanisms while genes are repaired very accurately. Plant mitochondrial genome rearrangements and repair errors lead to life-history trait changes such as male sterility, and our understanding of basic mechanisms of repair is currently inadequate for modeling and prediction of these processes and their outcomes. The central hypothesis of this project is that much of the DNA damage in mitochondria is processed through the various subtypes of double-strand break repair, leading to accurate repair of genes by gene conversion and repair of non-genes by inaccurate mechanisms including break-induced replication and non-homologous end-joining. This hypothesis will be tested by altering the repair pathways such that mismatches or double-strand breaks are created at known positions within the Arabidopsis thaliana mitochondrial genome, both in coding and noncoding DNA, and assessing which repair pathways have been used. This will lead to better understanding of the mechanisms and pathways of DNA repair and recombination in plant mitochondria. This work will also advance our knowledge of the mechanisms and theoretical underpinnings of evolutionary change in the mitochondrial genome. In addition, this project will provide training opportunities for graduate, undergraduate and high-school students from diverse backgrounds.