Site-recognition of RNA editing in chloroplasts

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1. RNA editing sites(1) Two additional sites were identified in the ndhD mRNA from tobacco (N. tabacum) chloroplasts. The total number of sites is thus 38, the most so far found in higher plant chloroplasts.(2) ACG to AUG RNA editing in ndhD mRNAs from tobacco progenitors (N sylvestris and N. tomentosiformis) was reexamined, and this editing in the latter species occurred depending on culture conditions.2. Improvement of the in vitro RNA editing assayA rapid and simple in vitro assay was established using fluorescent dideoxynucleotides.3. Cis-elements for RNA editingUsing the above assay, editing activities of 19 sites in five tobacco ndh mRNA species were measured. A cis-element in the ndhB mRNA was defined to be 5 nucleotides (nt) from-6 to-10, whereas ndhF mRNAs have two separate cis-elements, 15 nt from-1 to-15 and 5 nt from-36 to-40.4. Trans-factorsUsing fuorescent mRNAs, a method to detect trans-factors for editing was tried.5. Analysis of site-recognition factorsThe 56 kD trans-factor for psbE mRNA editing was isolated, and its partial amino acid sequences were determined. No similar sequence was found in databases.