Recent advances in the study of chloroplast gene expression and its evolution

Yusuke Yagi,Takashi Shiina

doi:10.3389/fpls.2014.00061

Yusuke Yagi, Takashi Shiina

Open Access

https://doi.org/10.3389/fpls.2014.00061

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Abstract

Chloroplasts are semiautonomous organelles which possess their own genome and gene expression system. However, extant chloroplasts contain only limited coding information, and are dependent on a large number of nucleus-encoded proteins. During plant evolution, chloroplasts have lost most of the prokaryotic DNA-binding proteins and transcription regulators that were present in the original endosymbiont. Thus, chloroplasts have a unique hybrid transcription system composed of the remaining prokaryotic components, such as a prokaryotic RNA polymerase as well as nucleus-encoded eukaryotic components. Recent proteomic and transcriptomic analyses have provided insights into chloroplast transcription systems and their evolution. Here, we review chloroplast-specific transcription systems, focusing on the multiple RNA polymerases, eukaryotic transcription regulators in chloroplasts, chloroplast promoters, and the dynamics of chloroplast nucleoids.

Highlights

Chloroplasts are believed to have arisen from an endosymbiotic event between a photosynthetic cyanobacterium and the ancestral eukaryotic cell
Chloroplast gene expression is mediated by two distinct types of RNA polymerase (RNAP) and is highly dependent on post-transcriptional regulation, such as the processing of polycistronic transcripts, intron splicing and RNA editing
THE LARGE TRANSCRIPTION COMPLEX IN HIGHER PLANT CHLOROPLASTS Two types of plastid-encoded plastid RNAP (PEP)-containing preparation have been biochemically isolated in mustard and Arabidopsis: soluble RNAP and plastid transcriptionally active chromosome attached to chloroplast membranes (Hess and Borner, 1999)

Summary

Introduction

Chloroplasts are believed to have arisen from an endosymbiotic event between a photosynthetic cyanobacterium and the ancestral eukaryotic cell. Basic chloroplast gene expression is mediated by prokaryotic machineries derived from the ancestral cyanobacterium, chloroplasts lost their homologs of bacterial regulatory elements such as transcription factors (TFs) and nucleoid proteins at an early stage of their evolution. Recent analyses of the chloroplast nucleoid proteins identified many non-bacterial components that play critical roles in chloroplast gene expression including transcription, post-transcriptional RNA processing, and translation.

Results

Conclusion