The cytoplasm of a multicellular eukaryote is a surprisingly dynamic entity with complex inter-organellar circuitries that influence nearly all aspects of cellular function, metabolism and programmed death. This complexity, together with a paucity of powerful model systems for study, has hindered progress in understanding the underlying mechanics of mitochondrial behavior. Our focus in this project is on the nuclear direction of mitochondrial genome maintenance, sorting and inheritance in Arabidopsis. We have identified several putative components of these processes, and we intend to study their function and regulation. The central hypothesis is that mitochondrial sorting and inheritance behavior derives from epigenetic and gamete-specific regulation of nuclear-encoded mitochondrial DNA maintenance and transmission loci. We will investigate the function of eight loci likely involved in DNA replication, sorting, recombination and inheritance processes using mutation and transgenic analysis. We will investigate their regulation using ectopic expression and in situ hybridization approaches, complemented with genetic approaches that incorporate enhancer and gene trap resources in Arabidopsis. As an outcome of this work we expect to determine the function of the selected loci in mitochondrial genome maintenance, and to characterize the nature of their regulation during reproductive development. This information is of fundamental importance to our understanding of nuclear-cytoplasmic interactions in higher eukaryotes. Data derived from this study would impact our understanding of imprinting and gene regulatory processes likely essential to successful in vitro fertilization technologies. Moreover, our project participates in the Young Nebraska Scientist training effort to enhance opportunities to recruit outstanding minority and underprivileged high school students to the life sciences by providing summer internship experiences in interesting and technically diverse project formats.
