Multiple organellar RNA editing factor (MORF) family proteins are required for RNA editing in mitochondria and plastids of plants

Abstract

Fig. 2. The MORF family of proteins contains nine genes and a potential pseudogene in A. thaliana. (A) The cladogram of similarities between the MORF proteins shows that the plastid editing factors MORF2 and MORF9 are rather distant from each other and more similar to the mitochondrial proteins MORF3 and MORF1, respectively. Predictions (marked mt or cp) and experimental data obtained by GFP-fusion protein localization (only MORF2) or proteomics MS data (marked with an asterisk) for the respective organellar locations are indicated. The MORF8 protein encoded by At3g15000 has been found in mitochondria in three independent assays. Proteins investigated here for their function are boxed. The conserved ∼100-amino acids domain is shaded; the other sequences show much less conservation (SI Appendix, Fig. S2). The potential pseudogene (At1g53260) contains only the C-terminal part of this conserved region. (B) Exon structures of the MORF3, MORF4 and MORF6 genes are similar to the MORF1 locus and contribute similar fragments but differ in their C-terminal extensions. MORF3 is a mitochondrial editing factor involved at more than 40 sites. Locations of the T-DNA insertions in mutants morf3-1, morf4-1, and morf6-1 are shown. LB denotes the location of the left border of the T-DNA. (C) Numbers of editing sites affected by T-DNA insertions in the respective MORF genes. In mutants morf4-1 and morf6-1, only one noncoding site each shows somewhat reduced editing.

An RNA recognition motif-containing protein is required for plastid RNA editing in Arabidopsis and maize

“…4C). We examined the organelle transcriptome of the mutant for editing defects because other proteins carrying RIP domains have been shown to be editing factors (19,20). We analyzed the plastid RNA editing extent with a new methodology based on RNA-seq.…”

“…A blastp search for homologs to the RIP1 protein returned the 10 previously reported members of the RIP family (19,20) as well as a unique RIP family member, encoded by the gene At3g20930 (Fig. 1A).…”

“…1A). This protein was not previously described as either a RIP or MORF protein (19,20). We used the MEME software (22) to identify four highly significant motifs in the RIP family (Fig.…”

“…Binding of the cis-element and the PPR-PLS trans-factor has been demonstrated in several instances (35)(36)(37). Recent reports have demonstrated that RIPs, another small class of proteins, are also plant organelle editing transfactors (19,20). Although the molecular function of the RIPs remains unknown, they are essential components of the plant RNA editing machinery; rip mutants exhibit severe defects in organelle editing.…”

“…RIP1 is a member of a small protein family that contains 10 members. Other members of the RIP family have also been shown to be required for organelle editing (20). RIP proteins are able to interact selectively with PPR trans-actors and also with each other (19,20); however, their function in the plant editosome remains unclear.…”