The Arabidopsis PPR protein EMB1006 interacts with both EMB1270 and CFM2 to facilitate plastidclpP1intron2 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.