A PPR Protein ACM1 Is Involved in Chloroplast Gene Expression and Early Plastid Development in Arabidopsis.

Yaqi An,Ye Li,Xinwei Wang,Jianwei Xiao

doi:10.3390/ijms22052512

Abstract

Chloroplasts cannot develop normally without the coordinated action of various proteins and signaling connections between the nucleus and the chloroplast genome. Many questions regarding these processes remain unanswered. Here, we report a novel P-type pentatricopeptide repeat (PPR) factor, named Albino Cotyledon Mutant1 (ACM1), which is encoded by a nuclear gene and involved in chloroplast development. Knock-down of ACM1 transgenic plants displayed albino cotyledons but normal true leaves, while knock-out of the ACM1 gene in seedlings was lethal. Fluorescent protein analysis showed that ACM1 was specifically localized within chloroplasts. PEP-dependent plastid transcript levels and splicing efficiency of several group II introns were seriously affected in cotyledons in the RNAi line. Furthermore, denaturing gel electrophoresis and Western blot experiments showed that the accumulation of chloroplast ribosomes was probably damaged. Collectively, our results indicate ACM1 is indispensable in early chloroplast development in Arabidopsis cotyledons.

Highlights

Chloroplast gene expression is vital for the chloroplast development process, which is mediated by two distinct types of RNA polymerases; plastid-encoded RNA polymerase (PEP) and nuclear-encoded RNA polymerases (NEP) [5,6]
In order to further study the molecular biosynthesis mechanism and development regulation of chloroplasts, we screened a series of T-DNA insertion lines related to chloroplast development defects from the Arabidopsis Biological Resource Center (ABRC)
We identified a novel factor that affected the chloroplast development in cotyledons of Arabidopsis

Summary

Introduction

Chloroplasts are well known as the most important organelle in higher plants. The chloroplast is generally considered to have originated through endosymbiosis with species of cyanobacteria. The process of chloroplast biogenesis and development is highly complex and ordered; while the molecular mechanisms have not been fully elucidated yet [3]. Development of the chloroplast involves an intricate interplay between both the chloroplast and the nuclear-cytoplasmic synthetic systems. A lot of signaling between the nucleus and chloroplast occurs to guide the proper formation and assembly of functional and photosynthetically active chloroplasts [4]. Chloroplast gene expression is vital for the chloroplast development process, which is mediated by two distinct types of RNA polymerases; plastid-encoded RNA polymerase (PEP) and nuclear-encoded RNA polymerases (NEP) [5,6]

Methods

Results

Discussion

Conclusion