Mono‐ and dicotyledonous plant‐specific RNA editing sites are correctly edited in both in organello systems

Abstract

We set out to analyse the phylogenetic distribution of cox2 RNA editing sites. Database searches have revealed the presence of mono-and dicotyledonous-specific RNA editing sites. Therefore, to better understand tRNA editing system in plants, we developed a new dicotyledonous in organello RNA editing system using cauliflower mitochondria and analysed the transcription of the cox2 gene for both maize and Arabidopsis. These results were compared with those obtained from a maize mitochondrial in organello system. Surprisingly, both the monoand dicotyledonous cox2 transcripts were efficiently edited in the mitochondrial cauliflower and maize in organello systems, respectively, even for RNA editing sites not present in the endogenous cox2 sequences. Taken together, our observations support a self-guiding-transcript model for RNA editing in higher plants.

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

“…Using the previously established in organello systems with maize (Staudinger and Kempken 2003) and cauliflower mitochondria (Bolle and Kempken 2006), the general ability of the mitochondria to process mRNAs was tested with mitochondrial A. thaliana and Z. mays cox2 constructs. In all cases, we observed full RNA processing of cox2 transcripts, i.e., splicing and editing (not shown) proving the mitochondria being fully active.…”

“…Using these in organello systems we are able to provide here the first direct evidence that plastid group II introns are not spliced from RNAs in isolated plant mitochondria nor is there any evidence for RNA editing. These results are discussed with respect to recent data regarding the mechanism of RNA editing site recognition in plant mitochondria (Bolle and Kempken 2006).…”

“…The vectors pTJ246 and pNB475, containing the cox2 gene from A. thaliana and the cox2-coding sequence including the intron from maize, respectively, were described in previous studies (Staudinger and Kempken 2003;Bolle and Kempken 2006).…”

“…While pentatricopeptide repeat (PPR) proteins are known to be involved in editing site selection in plastids (Kotera et al 2005;Okuda et al 2006Okuda et al , 2007, factors binding the cis-elements of mitochondrial RNA editing sites have not yet been identified. However, we have recently presented data that support a self-guiding-transcript model for RNA editing in mitochondria of higher plants, indicating that such factors may not be needed (Bolle and Kempken 2006). In this model the editing information is contained in the transcript itself, and the ability to edit editing sites would be based on the structural formation of the RNA transcript.…”

“…Up to now, no transformation system for plant mitochondria has been established. Therefore, we set out to use the previously established mitochondrial in organello editing systems (Staudinger and Kempken 2003;Bolle and Kempken 2006) to investigate the ability of plant mitochondria to recognize and edit plastid transcripts. In the previous studies we have shown that transcripts from introduced Arabidopsis thaliana cox2 and Zea mays cox2 were efficiently spliced and edited in the heterologous maize and cauliflower mitochondria.…”