Abstract
RNA editing is essential for compensating for defects or mutations in haploid organelle genomes and is regulated by numerous trans-factors. Pentatricopeptide repeat (PPR) proteins are the prime factors that are involved in RNA editing; however, many have not yet been identified. Here, we screened the plastid-targeted PLS-DYW subfamily of PPR proteins belonging to Arabidopsis thaliana and identified ORGANELLE TRANSCRIPT PROCESSING 970 (OTP970) as a key player in RNA editing in plastids. A loss-of-function otp970 mutant was impaired in RNA editing of ndhB transcripts at site 149 (ndhB-C149). RNA-immunoprecipitation analysis indicated that OTP970 was associated with the ndhB-C149 site. The complementation of the otp970 mutant with OTP970 lacking the DYW domain (OTP970∆DYW) failed to restore the RNA editing of ndhB-C149. ndhB gene encodes the B subunit of the NADH dehydrogenase-like (NDH) complex; however, neither NDH activity and stability nor NDH-PSI supercomplex formation were affected in otp970 mutant compared to the wild type, indicating that alteration in amino acid sequence is not necessary for NdhB function. Together, these results suggest that OTP970 is involved in the RNA editing of ndhB-C149 and that the DYW domain is essential for its function.
Highlights
RNA editing is considered an indirect repair strategy that is required for the functional expression of organelle genomes [1]
RNA Editing at the ndhB-C149 Site Is Impaired in otp970 Mutant Plant
The results showed defective RNA editing at the ndhB-C149 site in the otp970 mutant; this site was completely edited in wild-type plants but not in otp970 mutants (Figure 2D)
Summary
RNA editing is considered an indirect repair strategy that is required for the functional expression of organelle genomes [1]. In terms of the conversion of C to U, the protein product of mature RNA following RNA-editing is different from that encoded by the genomic. DNA, which may be attributed to the fact that C residues undergoing RNA editing are predominantly located at the first or second positions of codons. It is usually possible for C-to-U RNA editing to generate a new start codon by altering ACG to AUG [5] or to introduce a termination codon by altering CGA/CAA to UGA/UAA [6], extending or shortening the open reading frames. C-to-U RNA editing was first discovered in mitochondria [7,8]
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