Young Seedling Stripe3 Encodes a Chloroplast-localized Multiple Organellar RNA Editing Factor Essential for Chloroplast RNA Editing and Splicing in Rice
摘要
Chloroplast RNA post-transcriptional regulation, including RNA editing, splicing, and stabilization, is essential for chloroplast biogenesis. Although numerous factors involved in plastid RNA metabolism have been identified, the regulatory networks and functional relationships among them remain largely elusive. Here, we characterized a rice mutant, young seedling stripe3 (yss3), which exhibits a distinct white stripe phenotype at the seedling stage accompanied by severe defects in chloroplast development. Map-based cloning and transgenic complementation assays revealed that the yss3 phenotype is caused by a mutation in the Multiple Organellar RNA Editing Factor 9 (OsMORF9) gene. Further analysis demonstrated that the yss3 mutant displays widespread defects in chloroplast RNA editing and in the splicing of multiple chloroplast group II introns. Moreover, yeast two-hybrid and bimolecular fluorescence complementation assays suggested that OsMORF9 interacts with OsDYW2 and OsCLB19, whose Arabidopsis homologs are core components of the chloroplast RNA editosome. Additionally, OsMORF9 interacts with OsSLA4, OsTHA8, and OsYSA; notably, OsTHA8 is a small P-type PPR protein implicated in both RNA editing and splicing. Collectively, these results establish that OsMORF9 acts as a central hub in chloroplast RNA processing.