The pentatricopeptide repeat protein EMB1270 interacts with CFM2 to splice specific group II introns in Arabidopsis chloroplasts

• Published in: Journal of integrative plant biology 2021-11, Vol.63 (11), p.1952-1966
• Main Authors: Zhang, Li, Chen, Jingli, Zhang, Liqun, Wei, Ying, Li, Yajuan, Xu, Xinyun, Wu, Hui, Yang, Zhong‐Nan, Huang, Jirong, Hu, Fenhong, Huang, Weihua, Cui, Yong‐Lan
• Format: Article
• Language: English
• Subjects: Arabidopsis; Arabidopsis - metabolism; Arabidopsis thaliana; Biosynthesis; chloroplast; Chloroplasts; Chloroplasts - metabolism; CRM Family Member 2; DNA, Chloroplast - metabolism; Electrophoretic mobility; EMB1270; Embryos; Gene Expression Regulation, Plant; Immunoprecipitation; intron splicing; Introns; Mutants; pentatricopeptide repeat protein; Phenotypes; Photosynthesis; Photosystem I; Photosystem II; Proteins; Ribonucleic acid; RNA; RNA Splicing; Splicing
• ISSN: 1672-9072; 1744-7909
• DOI: 10.1111/jipb.13165

ABSTRACT Chloroplast biogenesis requires the coordinated expression of chloroplast and nuclear genes. Here, we show that EMB1270, a plastid‐localized pentatricopeptide repeat (PPR) protein, is required for chloroplast biogenesis in Arabidopsis thaliana. Knockout of EMB1270 led to embryo arrest, whereas a mild knockdown mutant of EMB1270 displayed a virescent phenotype. Almost no photosynthetic proteins accumulated in the albino emb1270 knockout mutant. By contrast, in the emb1270 knockdown mutant, the levels of ClpP1 and photosystem I (PSI) subunits were significantly reduced, whereas the levels of photosystem II (PSII) subunits were normal. Furthermore, the splicing efficiencies of the clpP1.2, ycf3.1, ndhA, and ndhB plastid introns were dramatically reduced in both emb1270 mutants. RNA immunoprecipitation revealed that EMB1270 associated with these introns in vivo. In an RNA electrophoretic mobility shift assay (REMSA), a truncated EMB1270 protein containing the 11 N‐terminal PPR motifs bound to the predicted sequences of the clpP1.2, ycf3.1, and ndhA introns. In addition, EMB1270 specifically interacted with CRM Family Member 2 (CFM2). Given that CFM2 is known to be required for splicing the same plastid RNAs, our results suggest that EMB1270 associates with CFM2 to facilitate the splicing of specific group II introns in Arabidopsis. The pentatricopeptide repeat protein EMB1270 promotes splicing of specific group II introns in Arabidopsis chloroplasts via direct binding to these introns. EMB1270 interacts with CFM2, which is required for splicing the same plastid RNAs. This observation improves our understanding of the molecular mechanism of plastid RNA splicing.