The ATP Synthase γ Subunit ATPC1 Regulates RNA Editing in Chloroplasts.

RNA editing is the process of modifying RNA molecules by inserting, deleting, or substituting nucleotides. In flowering plants, RNA editing occurs predominantly in RNAs encoded by the organellar genomes of mitochondria and chloroplasts, and the main type of editing involves the substitution of cytidine with uridine at specific sites. Abnormal RNA editing in plants can affect gene expression, organelle function, plant growth, and reproduction. In this study, we report that ATPC1, the gamma subunit of ATP synthase in Arabidopsis chloroplasts, has an unexpected role in the regulation of editing at multiple sites of plastid RNAs. The loss of function of ATPC1 severely arrests chloroplast development, causing a pale-green phenotype and early seedling lethality. Disruption of ATPC1 increases the editing of matK-640, rps12-i-58, atpH-3'UTR-13210, and ycf2-as-91535 sites while decreasing the editing of rpl23-89, rpoA-200, rpoC1-488, and ndhD-2 sites. We further show that ATPC1 participates in RNA editing by interacting with known multiple-site chloroplast RNA editing factors, including MORFs, ORRM1, and OZ1. The transcriptome in the atpc1 mutant is profoundly affected, with a pattern of defective expression of chloroplast development-related genes. These results reveal that the ATP synthase γ subunit ATPC1 is involved in multiple-site RNA editing in Arabidopsis chloroplasts.