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

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.

Translational regulation in chloroplasts for development and homeostasis

“…Drastic increases in the rates of radioisotope pulse-labeling of PsbA, PsaA, PsaB, and the LSU of Rubisco were observed in isolated etioplasts as they underwent greening, while levels of the mRNAs encoding these proteins changed less [31][32][33]. This could be due to repression of the elongation phase of translation in the dark because ribosome occupancy on the initiation [163]. ATAB2 activates the translation of mRNAs encoding subunits of PSI and PSII in Arabidopsis (Section 2) [27].…”

Expression of the chloroplast genome: modern concepts and experimental approaches

“…Разные σ-факторы имеют конкретные функции в регу-ляции экспрессии генома пластид и отвечают за транс-крипцию определенного набора генов (Yagi, Shiina, 2014). Разнообразие σ-факторов и использование их растениями в зависимости от сигналов окружающей среды, стадий развития организма, типа пластид обеспечивает соответ-ствующую регуляцию транскрипции (Allison, 2000;Toyoshima et al, 2005;Liere, Börner, 2007;Lerbs-Mache, 2011).…”

Organellar Genomes of Flowering Plants

“…A wide range of proteins can be found in a nucleoid (Yagi and Shiina 2014 ), but this composition may vary at different time points as nucleoid is not an isolated structure, and its protein pool, which shows much fl exibility, could only be defi ned depending upon the functional state a nucleoid is in (Kuroiwa 1991 ). The proteins are tightly bound to the DNA in the central region, whereas they are loosely bound to the DNA fi brils in the peripheral nucleoid space (Hansmann et al 1985 ).…”

“…This category includes plastid-encoded RNA polymerase (PEP), PEP-associated proteins (PAP) and pentatricopeptide repeat proteins (PPR proteins) (Pfalz et al 2006 ). 70S ribosomes, ribosome assembly factors and many other proteins are associated with DNA replication, DNA repair and mRNA splicing, editing and translation (Yagi and Shiina 2014 ). The second category is of architectural ptNAPs -those involved in membrane anchoring and DNA compaction like PEND, PD1, PD3, MFP1, TCP34, pTAC16, SiR, CND41, YLMG1 and SWIB (Krupinska et al 2013 ).…”