A Plastid RNA Polymerase-Associated Protein Is Involved in Early Chloroplast Development in Rice

Abstract

Plastid-encoded RNA polymerase (PEP) regulates the expression of chloroplast genes involved in photosynthesis and chloroplast development in rice. The PEP-associated protein (PAP) PAP7/pTAC14 is essential for the formation of the PEP complex. However, the function of PAP7 in chloroplast development in rice remains unclear. In this study, we identified a mutant, w81, which displays a yellow-green leaf symptom before the four-leaf stage. The seedlings of the w81 mutant display reduced chlorophyll content, abnormal chloroplast structure, and elevated reactive oxygen species (ROS) level. After the four-leaf stage, plant leaves of the w81 mutant gradually turn green with increased chlorophyll content. Map-based cloning reveals that the PAP7 in the w81 mutant harbors a T to A single-base substitution. This mutation blocks the normal splicing of the fifth intron and generates 74 bp longer transcripts in the mutant. The OsPAP7 protein mainly localizes to the chloroplast and directly interacts with OsPAP5. Our results highlight that OsPAP7 regulates the expression of PEP-dependent chloroplast genes and plays a key role in chloroplast development in rice.