cis recognition elements in plant mitochondrion RNA editing

RNA editing in higher plant mitochondria modifies mRNA sequences by means o f C-to-U conversions at highly specific sites. To determine the cis element s involved in recognition of an editing site in plant mitochondria, deletio n and site-directed mutation constructs containing the cognate cox II mitoc hondrial gene were introduced into purified mitochondria by electroporation . The RNA editing status was analyzed for precursor and spliced transcripts from the test construct. We found that only a restricted number of nucleot ides in the vicinity of the target C residue were necessary for recognition by the editing machinery and that the nearest neighbor 3 ' residues were c rucial for the editing process. We provide evidence that two functionally d istinguishable sequences can be defined: the 16-nucleotide 5 ' region, whic h can be replaced with the same region from another editing site, and a 6-n ucleotide 3 ' region specific to the editing site. The latter region may pl ay a role in positioning the actual editing residue.