OsOZ1, a zinc finger motif-containing protein, is essential for chloroplast development through RNA editing and intron splicing in rice

Abstract The chloroplast is the primary organelle for photosynthesis in plants. A clade of proteins containing RanBP2-type zinc-finger domain, known as the Organelle Zinc (OZ) finger family, are known or predicted to be targeted to mitochondria or chloroplast. While some OZ proteins have been studied in Arabidopsis , there are few reports of their roles in rice. In this study, we characterized the Organelle Zinc finger family gene OsOZ1 and generated the oz1 mutants using the CRISPR-Cas9 genome editing system in rice. The oz1 mutants exhibited a seedling-lethal chlorosis phenotype, with a significantly reduced chlorophyll content at the third-leaf stage compared to the wild type. Transmission electron microscopy and quantitative real-time PCR analysis revealed that the oz1 mutants displayed abnormal chloroplast development relative to the wild type, along with significant alterations in gene expression levels related to chloroplast development and photosynthesis. The oz1 mutants demonstrated defects in chloroplast RNA editing, particularly in atpA-1148 , ndhB-467 , ndhB-586 , ndhB-737 and ndhB-830 , while the splicing of ndhA , trnG and ycf3-1 was significantly decreased in the oz1 mutants compared to the wild type. The yeast two-hybrid assay demonstrated that OsOZ1 interacts with the PPR protein OsSLC1, the ORRM protein OsORRM1 and the MORF/RIP protein OsMORF9. This suggests that OsOZ1 may form complexes with OsSLC1, OsORRM1 and OsMORF9, thereby participating in chloroplast RNA editing and splicing activities. Overall, these findings indicate that OsOZ1 plays a crucial role in chloroplast development by regulating the editing and splicing of chloroplast RNA in rice.