The PPR protein SLOW GROWTH 4 is involved in editing of nad4 and affects the splicing of nad2 intron 1
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SLO4 is a mitochondrial PPR protein that is involved in editing nad4, possibly required for the efficient splicing of nad2 intron1.
Pentatricopeptide repeat (PPR) proteins constitute a large protein family in flowering plants and are thought to be mostly involved in organellar RNA metabolism. The subgroup of PLS-type PPR proteins were found to be the main specificity factors of cytidine to uridine RNA editing. Identifying the targets of PLS-type PPR proteins can help in elucidating the molecular function of proteins encoded in the organellar genomes. In this study, plants lacking the SLOW GROWTH 4 PPR protein were characterized. Slo4 mutants were characterized as having restricted root growth, being late flowering and displaying an overall delayed growth phenotype. Protein levels and activity of mitochondrial complex I were decreased and putative complex I assembly intermediates accumulated in the mutant plants. An editing defect, leading to an amino acid change, in the mitochondrial nad4 transcript, encoding for a complex I subunit, was identified. Furthermore, the splicing efficiency of the first intron of nad2, encoding for another complex I subunit, was also decreased. The change in splicing efficiency could however not be linked to any editing defects in the nad2 transcript.
KeywordsMitochondria Complex I RNA editing Splicing Pentatricopeptide repeat
The authors would like to thank Prof. Ian Small from the University of Western Australia for assisting with prediction of PPR binding sites. This work was supported by the Deutsche Forschungsgemeinschaft.
SW and CC carried out all experimental work. SW, JS and CC were all involved in planning and designing experiments and all authors contributed to the writing of the manuscript.
Compliance with ethical standards
Conflict of interest
The authors declare no conflicts of interest. None of the research presented here involved human participants or animals.
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