Plastid mRNAs are neither spliced nor edited in maize and cauliflower mitochondrial in organello systems

The process of RNA editing in chloroplasts and higher plant mitochondria displays some similarities, raising the question of common or similar components in editing apparatus of these two organelles. To investigate the ability of plant mitochondria to edit plastid transcripts, we employed a previously established mitochondrial maize and cauliflower in organello system. Two plastid genes, Zea mays ndhB and ycf3 containing group II introns and several editing sites, were introduced into mitochondria. The genes were transcribed in organello. However, these transcripts of the plastid genes are neither spliced nor edited in plant mitochondria. A comparison of maize ndhB editing sites and maize mitochondrial editing sites reveals considerable sequence similarities between three ndhB editing sites and several mitochondrial sites. Nevertheless, these ndhB editing sites were not recognized in the mitochondria. Thus, we present for the first time direct evidence that the factors present in the plant mitochondria are not sufficient to allow editing and splicing of plastid transcripts.