Mitochondrial Alterations Associated with Cytoplasmic Male Sterility in Plant Development

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Growth and differentiation in nearly all eukaryotic cells depends on the metabolism and generation of energy by the mitochondrion. Proper functioning of the mitochondrion involves an integrated system of both nuclear and mitochondrial gene expression. Cytoplasmic male sterility is one system in which tissue-specific mitochondrial function and the role of nuclear factors on mitochondrial biogenesis can be studied. Previous studies have identifed alterations in two loci, atp6 and atpA, that may be involved with male steriltiy in Ogura radish. These alterations will be characterized further by the following experiments: 1. Western hybridization analysis, in organello translation, protein purification and NH2-terminal sequencing will be conducted to investigate: A) the abundance of the ATP6, ATPA and an Ogura- specific polypeptide, ORF105, B) the NH2-terminal sequence of ATP6, and C) the effect of nuclear restorer loci on their expression. 2. Biochemical and physiological studies (e.g. measurements of ATPase activities, mitochondrial respiratory rates and membrane potentials) will be conducted on mitochondria isolated from normal, and fertile and sterile Ogura radish plants in an attempt to identify in which processes Ogura mitochondria are dysfunctional and if there is any correlation with the putative alterations identified by molecular analysis. 3. Genetic and molecular approaches (e.g. analysis of recombinant mitochondrial genomes) will be utilized in an attempt to establish a genetic, casual relationship between altered mitochondrial sequences and cytoplasmic male sterility. The relationship between mitochondrial function and cytoplasmic male sterility not only allows an understanding of the cells "power plant", the mitochondria, but also will reveal basic information about the development of the pollination mechanism.