The plastid transcription machinery and its coordination with the expression of nuclear genome: Plastid-Encoded Polymerase, Nuclear-Encoded Polymerase and the Genomes Uncoupled 1-mediated retrograde communication

• Published in: Philosophical transactions of the Royal Society of London. Series B. Biological sciences 2020-06, Vol.375 (1801), p.20190399-20190399
• Main Authors: Tadini, Luca, Jeran, Nicolaj, Peracchio, Carlotta, Masiero, Simona, Colombo, Monica, Pesaresi, Paolo
• Format: Article
• Language: English
• Subjects: Cell Nucleus - genetics; Cell Nucleus - metabolism; Chloroplasts - genetics; Chloroplasts - physiology; DNA-Directed RNA Polymerases - genetics; DNA-Directed RNA Polymerases - metabolism; Gene Expression Regulation, Plant - physiology; Genome, Plant; Photosynthesis; Plant Proteins - genetics; Plant Proteins - metabolism; Plants - enzymology; Plants - genetics; Plastids - genetics; Plastids - metabolism; Review; Signal Transduction - genetics; Transcription, Genetic - physiology
• ISSN: 0962-8436; 1471-2970
• DOI: 10.1098/rstb.2019.0399

Plastid genes in higher plants are transcribed by at least two different RNA polymerases, the plastid-encoded RNA polymerase (PEP), a bacteria-like core enzyme whose subunits are encoded by plastid genes ( , , and ), and the nuclear-encoded plastid RNA polymerase (NEP), a monomeric bacteriophage-type RNA polymerase. Both PEP and NEP enzymes are active in non-green plastids and in chloroplasts at all developmental stages. Their transcriptional activity is affected by endogenous and exogenous factors and requires a strict coordination within the plastid and with the nuclear gene expression machinery. This review focuses on the different molecular mechanisms underlying chloroplast transcription regulation and its coordination with the photosynthesis-associated nuclear genes ( ) expression. Particular attention is given to the link between NEP and PEP activity and the GUN1- (Genomes Uncoupled 1) mediated chloroplast-to-nucleus retrograde communication with respect to the adaptive response, i.e. the increased accumulation of NEP-dependent transcripts upon depletion of PEP activity, and the editing-level changes observed in NEP-dependent transcripts, including and , in cotyledons after norflurazon or lincomycin treatment. The role of cytosolic preproteins and HSP90 chaperone as components of the GUN1-retrograde signalling pathway, when chloroplast biogenesis is inhibited in cotyledons, is also discussed. This article is part of the theme issue 'Retrograde signalling from endosymbiotic organelles'.