The Arabidopsis PPR protein EMB1006 interacts with both EMB1270 and CFM2 to facilitate plastid clpP1 intron2 splicing

Plastid intron splicing is an essential step for gene expression. Although many nucleus-encoded splicing factors have been identified for plastid intron splicing, how these proteins coordinately regulate intron splicing is unclear. Here we found that EMB1006, an Arabidopsis P-type PPR protein, is required for splicing several plastid introns including clpP1 intron 2 by analyzing the level of intron retention in its knockdown lines and RIP-qPCR (RNA immunoprecipitation and quantitative PCR) assay. In addition, RNA electrophoretic mobility shift assay (REMSA) showed that EMB1006 specifically binds to the sequence UUACCAAACGU close to the 3 end of clpP1 exon 2 in vitro. Furthermore, yeast two hybrid (Y2H), split luciferase complementation (Split-LUC) and semi-in vivo pull-down assays showed that EMB1006 interacts with both EMB1270 and CFM2, which also interact each other. Taken together, our data indicate that EMB1006 forms a complex with EMB1270 and CFM2 to facilitate clpP1 intron 2 splicing in chloroplasts.