Collaborative Research: Paternal Transmission and Recombination of the Mitochondrial Genome in the Plant Genus Silene

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This research project will expand our understanding of the causes and consequences of an unusual form of inheritance in plants, the transmission of organelles through pollen. A defining feature of cells with nuclei is the existence of organelles that have separate genomes. The nuclear genome is generally inherited from two parents. By contrast, the genomes of organelles, such as those in mitochondria, are nearly always inherited from the mother only. However, we know little about the frequency and cause of deviations from this general rule. Understanding the inheritance of organelle genomes is therefore important for understanding evolutionary processes. Using the plant Silene vulgaris as a model system, this project will explore the relationship between the geographic origins of the nuclear genome and paternal mitochondrial transmission, and the relationship between the physical structure of the mitochondrial genome and the propensity for mitochondrial genes to recombine. This requires 1) sequencing several S. vulgaris mitochondrial genomes to document genome structure and identify genetic markers used to study recombination, 2) genotyping individuals from natural populations in order to estimate recombination, 3) conducting experimental crosses between individuals of varying nuclear and mitochondrial genotypes, and 4) genotyping their offspring to identify incidences of mitochondrial paternal inheritance. In addition to furthering fundamental knowledge of plant mitochondrial genome biology, the results should be of applied significance. Plant breeders are concerned with developing CMS (cytoplasmic male sterility) resources because utilization of male-sterile individuals in breeding programs increases efficiency, and CMS genes usually reside in the mitochondrial genome. Studies of the inheritance of organellar genomes are also valuable because of concerns about gene escape from genetically modified organisms.