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 chloroplasts and the nucleus in flowering plants, 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 chloroplast multiple-site RNA editing factors MORF2 and MORF9 and participates in RNA editing by modulating their dimerization. Taken together, our work indicates that the important retrograde signaling regulator HDS also plays a novel role in chloroplast RNA editing, providing insight into the connection between organelle-to-nucleus communication and RNA metabolism in chloroplasts.