Disturbed RNA editing in MORF3-deficient Arabidopsis mitochondria leads to impaired assembly of complex I

Area of Science:

• Plant molecular biology
• Mitochondrial gene expression
• RNA editing mechanisms

Background:

• Plant mitochondria and chloroplasts edit transcripts before translation.
• RNA editing is crucial for gene expression, potentially compensating for mutations and regulating protein function.
• The precise roles and consequences of RNA editing, especially in mitochondrial respiration, require further investigation.

Purpose of the Study:

• To characterize proteins translated from unedited mitochondrial transcripts in Arabidopsis thaliana.
• To investigate the impact of reduced RNA editing on mitochondrial function and protein complex assembly.
• To identify specific RNA editing sites critical for the proper assembly of respiratory chain complexes.

Main Methods:

• Utilized a multiple organellar RNA editing factor 3 (MORF3) mutant exhibiting reduced RNA editing.
• Performed physiological and biochemical analyses to assess respiratory chain complex function.
• Employed shotgun proteomics and complexome profiling to identify and quantify proteins and their assembly states.

Main Results:

• The MORF3 mutant displayed developmental delays but remained fertile.
• Complex I of the respiratory chain was significantly affected in the mutant.
• Proteomic analysis identified proteins from unedited nad2 and nad7 transcripts, which integrated into complex I and supercomplexes, with enriched assembly intermediates.

Conclusions:

• Disruption of complex I assembly is linked to unedited transcripts encoding Nad3 and Nad4L subunits.
• This study provides insights into the molecular consequences of impaired RNA editing on mitochondrial respiratory complex I assembly.
• RNA editing is essential for the correct assembly and function of plant mitochondrial respiratory complexes.