Arabidopsis 2010: Mitochondrial RNA Editing in Arabidopsis thaliana

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Intellectual Merit: RNA editing is a process that alters the genetic information at specific sites on RNA molecules. Editing has been described in a wide range of organisms from viruses to animals and plants. In vascular plants, organelle transcripts are modified after synthesis by cytosine-to-uracil (C-to-U) editing. Although RNA editing has been studied extensively in some systems, in plants, many questions still remain. For example, neither the chloroplast nor mitochondrial editing enzyme that performs the actual nucleotide alteration has been discovered. Also, despite the importance of nucleotide selectivity in preventing chaotic, unproductive alteration of RNAs, little is known about the mechanisms responsible for selecting specific nucleotides to be modified. This project seeks to deepen understanding of plant RNA editing by identifying proteins that are involved in mitochondrial editing. In prior work, natural variation in Arabidopsis combined with genetic analysis allowed the mapping of quantitative trait loci (QTLs) that control differential editing extent at specific C targets of editing in two Arabidopsis lines. Candidate editing genes in the QTL intervals will be tested for their possible involvement in editing of specific C targets by virus-induced gene silencing (VIGS). Knock-out mutants in editing genes identified by the VIGS screen will be sought from publicly available mutant collections. Immunoprecipitation or affinity tagging experiments with mutant and normal plants will be used to identify components of the molecular machine that performs mitochondrial RNA editing.Broader Impact: Mitochondria are essential organelles in plants that are critical for energy transduction. Plant mitochondrial gene expression is profoundly affected by the RNA editing process, which modifies as many as 500 Cs encoded in the genome. Identifying the nuclear genes that are responsible for encoding proteins that perform RNA editing is essential to our understanding of mitochondrial biogenesis. This project will provide research experiences for 8-12 undergraduates over the next three years, including underrepresented minority students participating in an NSF REU program.