RNA editing competence of trans-factor MEF1 is modulated by ecotype-specific differences but requires the DYW domain

RNA editing in plant mitochondria posttranscriptionally changes multiple cytidines to uridines. The RNA editing trans-factor MEF1 was identified via ecotype-specific editing polymorphisms in Arabidopsis thaliana. Complementation assays reveal that none of the three amino acid changes between Columbia (Col) and C24 individually alters RNA editing. Only one combination of these polymorphisms lowers editing at two of the three target sites, suggesting additive effects of the involved SNPs. Functional importance of the C-terminal DYW domain was analysed with DYW-truncated and extended constructs. These do not recover RNA editing in protoplasts and regain only low levels in stable transformants. In MEF1, the DYW domain is thus required for full competence in RNA editing and its C-terminus has to be accessible.