The isoprenoid biosynthesis enzyme HDS participates in chloroplast RNA editing

Post-transcriptional RNA editing and retrograde signaling in chloroplasts are crucial for coordinating gene expression between the chloroplasts and the nucleus in flowering plants, and yet the molecular link between them remains poorly understood. This study reveals that the Arabidopsis isoprenoid biosynthesis enzyme 1-hydroxy-2-methyl-2-(E)-butenyl-4-diphosphate synthase (HDS), a known regulator of retrograde signaling, is also involved in chloroplast RNA editing. We found that the loss of HDS function significantly altered RNA editing efficiency at multiple specific sites in chloroplast transcripts. HDS mutants exhibited a pale phenotype and early seedling lethality, with severely impaired chloroplast development and photosynthetic apparatus assembly. Moreover, we demonstrated that HDS physically interacts with the chloroplast multiple-site RNA-editing factors MORF2 and MORF9 and participates in RNA editing by modulating their dimerization. Taken together, our results indicate that the important retrograde signaling regulator HDS also plays a novel role in chloroplast RNA editing, providing insights into the connection between organelle-to-nucleus communication and RNA metabolism in chloroplasts.