Studies of plant nuclear-mitochondrial genetic interactions

The genetic system of mitochondria is largely under the control of the nuclear genome. In plants, efforts to study nuclear-mitochondrial interactions are complicated by the indispensability of mitochondrial function; mutations that lead to mitochondrial dysfunction are generally lethal. In this study, a unique model system, CMS common bean (Phaseolus vulgris L.), carrying a non-lethal mitochondrial mutation, was explored to investigate how a nuclear gene, Fr, affects the mitochondrial genome structure to restore a male-fertile phenotype. As a first step toward molecular cloning of Fr, a genetic linkage map of the Fr region was established. Genetic approaches were taken to investigate the mode and mechanism of Fr action in altering the heteroplasmic mitochondrial population. Finally, the CMS-associated mitochondrial gene, pvs-orf239, was expressed in transgenic tobacco plants to provide definitive evidence for its role in causing male sterility and to elucidate the mechanism of pollen disruption