OsPPR9 encodes a DYW-type PPR protein that affects editing efficiency of multiple RNA editing sites and is essential for chloroplast development

Photosynthesis occurs mainly in chloroplasts, whose development is regulated by proteins encoded by nuclear genes.  Among them, pentapeptide repeat (PPR) proteins participate in organelle RNA editing.  Although there are more than 450 members of the PPR protein family in rice, only a few affect RNA editing in rice chloroplasts.  Gene editing technology has created new rice germplasm and mutants, which could be used for rice breeding and gene function study.  This study evaluated the functions of OsPPR9 in chloroplast RNA editing in rice.  The osppr9 mutants were obtained by CRISPR/Cas9, which showed yellowing leaves and a lethal phenotype, with suppressed expression of genes associated with chloroplast development and accumulation of photosynthetic-related proteins.  In addition, loss of OsPPR9 protein function reduces the editing efficiency of rps8-C182, rpoC2-C4106, rps14-C80, and ndhB-C611 RNA editing sites, which affects chloroplast growth and development in rice.  Our data showed that OsPPR9 is highly expressed in rice leaves and encodes a DYW-PPR protein localized in chloroplasts.  Besides, the OsPPR9 protein was shown to interact with OsMORF2 and OsMORF9.  Together, our findings provide insights into the role of the PPR protein in regulating chloroplast development in rice.