PPR647 Protein Is Required for Chloroplast RNA Editing, Splicing and Chloroplast Development in Maize

Chloroplasts play an essential role in plant growth and development. Any factors affecting chloroplast development will lead to abnormal plant growth. Here, we characterized a new maize mutant, albino seedling mutant 81647 (as-81647), which exhibits an entirely albino phenotype in leaves and eventually died before the three-leaf stage. Transmission electron microscopy (TEM) demonstrated that the chloroplast thylakoid membrane was impaired and the granum lamellae significantly decreased in as-81647. Map-based cloning and transgenic analysis confirmed that PPR647 encodes a new chloroplast protein consisting of 11 pentratricopeptide repeat domains. Quantitative real-time PCR (qRT-PCR) assays and transcriptome analysis (RNA-seq) showed that the PPR647 mutation significantly disrupted the expression of PEP-dependent plastid genes. In addition, RNA splicing and RNA editing of multiple chloroplast genes showed severe defects in as-81647. These results indicated that PPR647 is crucial for RNA editing, RNA splicing of chloroplast genes, and plays an essential role in chloroplast development.