Intellectual merit: Plant mitochondrial genomes are surprisingly different from those of animals and fungi. They are also involved in such diverse and important processes as plant growth, flowering and seed set. A significant technological gap in the study of plant physiology and genetics is the inability to transform plant mitochondria. Although it has not been accomplished in the laboratory, horizontal gene transfer between mitochondria of different plant species is evidence that foreign DNA can be incorporated into the mitochondrial genome. A new understanding of recombination mechanisms suggests two novel approaches to the problem: using large homologous regions for targeting, or transforming a mutant defective in recombination homology surveillance. This research will enable new approaches to plant biology and biotechnology that are currently impossible. Three important phases of achieving transformation will be done. These are to engineer the bacterium Agrobacterium tumefaciens to target introduced DNA to mitochondria, to use large regions of homology for recombination targeting, and the choice of selectable markers. This project will use multiple approaches to the selectable marker problem, including both endogenous and exogenous genes. Broader impacts: This project will have a tremendous impact on the research infrastructure for plant mitochondrial biology. This will dramatically open up the field to new experimental directions and new advances, both for basic biology and in agriculturally important plants. The project will involve an undergraduate research training experience in the summer, and there will be an emphasis on broadening participation. A high school student and teacher training effort at the institution will be incorporated, and the institution also sponsors an undergraduate summer internship program that will be integrated into the project.