WHITE STRIPE LEAF4 Encodes a Novel P-Type PPR Protein Required for Chloroplast Biogenesis during Early Leaf Development.

Ying Wang,Jianmin Wan,Linglong Liu,Yunlong Wang,Kunneng Zhou,Xin Zhang,Long Zhang,Zhiming Feng,Jiulin Wang,Cailin Lei,Liwei Wang,Weiwei Ma,Yang Xu,Xiuping Guo,Yulong Ren,Huan Zhang,Zhijun Cheng

doi:10.3389/fpls.2017.01116

Abstract

Pentatricopeptide repeat (PPR) proteins comprise a large family in higher plants and perform diverse functions in organellar RNA metabolism. Despite the rice genome encodes 477 PRR proteins, the regulatory effects of PRR proteins on chloroplast development remains unknown. In this study, we report the functional characterization of the rice white stripe leaf4 (wsl4) mutant. The wsl4 mutant develops white-striped leaves during early leaf development, characterized by decreased chlorophyll content and malformed chloroplasts. Positional cloning of the WSL4 gene, together with complementation and RNA-interference tests, reveal that it encodes a novel P-family PPR protein with 12 PPR motifs, and is localized to chloroplast nucleoids. Quantitative RT-PCR analyses demonstrate that WSL4 is a low temperature response gene abundantly expressed in young leaves. Further expression analyses show that many nuclear- and plastid-encoded genes in the wsl4 mutant are significantly affected at the RNA and protein levels. Notably, the wsl4 mutant causes defects in the splicing of atpF, ndhA, rpl2, and rps12. Our findings identify WSL4 as a novel P-family PPR protein essential for chloroplast RNA group II intron splicing during early leaf development in rice.

Highlights

Chloroplasts, thought to have originated from cyanobacteria through endosymbiosis, are the exclusive organelles for photosynthesis in plants and algae, and have important roles in synthesis and storage of many key metabolites, such as lipids, terpenoids, and amino acids (Mullet, 1993; Moreira et al, 2000; Sugimoto et al, 2004)
We show that WSL4 encodes a novel P-family pentatricopeptide repeat (PPR) protein that targets to the chloroplast nucleoid
The results showed that the editing efficiency of rpoB at C545 and C560 exhibited a significant increase in wsl4 mutant compared with wild type (WT) (Figure 7), while the rest 11 genes and the corresponding 19 editing sites were normally edited in wsl4 mutant (Supplementary Figure S5)

Summary

Introduction

Chloroplasts, thought to have originated from cyanobacteria through endosymbiosis, are the exclusive organelles for photosynthesis in plants and algae, and have important roles in synthesis and storage of many key metabolites, such as lipids, terpenoids, and amino acids (Mullet, 1993; Moreira et al, 2000; Sugimoto et al, 2004). Chloroplast development from proplastids is subdivided into three stages; that are coordinately regulated by both plastidand nuclear-encoded genes (Kusumi et al, 2004; Munekage et al, 2004; Jarvis and Lopez-Juez, 2013; Kusumi and Iba, 2014; Pogson et al, 2015). The second step known as the chloroplast “build-up” stage establishes the chloroplast genetic system, in which a nuclear-encoded plastid RNA polymerase (NEP) preferentially transcribes genes encoding plastid gene expression machinery that promotes the transcription and translation in chloroplasts (Hajdukiewicz et al, 1997). Plastid genes, predominantly transcribed by a plastid-encoded plastid RNA polymerase (PEP), in combination with imported nuclear-encoded proteins, constitute the photosynthetic and metabolic machinery to control chloroplast development (Kanamaru et al, 1999). Cloning and characterization of such nuclear genes should help elucidate the complex regulatory mechanisms of chloroplast development in plants

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