XVI International Botanical Congess

RNA editing in higher plant chloroplasts is C-to-U conversion which results in the acquisition of conserved amino acids. Editing also creates initiation or termination codons. We have identified 31 editing sites in tobacco chloroplast transcripts, however, no consensus sequence could be observed in the region of spanning editing sites. In order to elucidate the molecular mechanism of RNA editing in chloroplasts, we have developed an in vitro RNA editing system from tobacco chloroplasts. Using the in vitro system, we defined cis-elements for editing of psbL and ndhB mRNAs. Competition analysis revealed that site specific trans-factors interact with cis-elements. Micrococcal nuclease treatment of chloroplast extracts did not affect editing, suggesting that no RNA factors are required. We previously isolated a set of chloroplast RNA binding proteins with typical RNA recognition motifs from tobacco chloroplasts. Immunological experiments suggested that one of these RNA binding proteins is involved in editing. From these data, we propose a model for RNA editing in chloroplasts.