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A Nucleus-Encoded Chloroplast Phosphoprotein Governs Expression of the Photosystem I Subunit PsaC in Chlamydomonas reinhardtii

Qu, Yujiao
Johnson, Xenie
Schmitz-Linneweber, Christian
Published in The Plant cell. 2016, vol. 28, no. 5, p. 1182-1199
Abstract The nucleo-cytoplasmic compartment exerts anterograde control on chloroplast gene expression through numerous proteins that intervene at posttranscriptional steps. Here, we show that the maturation of psaC mutant (mac1) of Chlamydomonas reinhardtii is defective in photosystem I and fails to accumulate psaC mRNA. The MAC1 locus encodes a member of the Half-A-Tetratricopeptide (HAT) family of super-helical repeat proteins, some of which are involved in RNA transactions. The Mac1 protein localizes to the chloroplast in the soluble fraction. MAC1 acts through the 5' untranslated region of psaC transcripts and is required for their stability. Small RNAs that map to the 5'end of psaC RNA in the wild type but not in the mac1 mutant are inferred to represent footprints of MAC1-dependent protein binding, and Mac1 expressed in bacteria binds RNA in vitro. A coordinate response to iron deficiency, which leads to dismantling of the photosynthetic electron transfer chain and in particular of photosystem I, also causes a decrease of Mac1. Overexpression of Mac1 leads to a parallel increase in psaC mRNA but not in PsaC protein, suggesting that Mac1 may be limiting for psaC mRNA accumulation but that other processes regulate protein accumulation. Furthermore, Mac 1 is differentially phosphorylated in response to iron availability and to conditions that alter the redox balance of the electron transfer chain.
PMID: 27113776
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Research groups Institute of Biology, Molecular Genetics, Humboldt University of Berlin; Unité Mixte de Recherche 7141, CNRS/Université Pierre et Marie Curie, Paris
Groupe Goldschmidt-Clermont
Swiss National Science Foundation: 31003A_146300
Swiss National Science Foundation: 31003A_146300 and 3100A0-117712
European Commission: SUNBIOPATH
(ISO format)
DOUCHI, Damien et al. A Nucleus-Encoded Chloroplast Phosphoprotein Governs Expression of the Photosystem I Subunit PsaC in Chlamydomonas reinhardtii. In: The Plant cell, 2016, vol. 28, n° 5, p. 1182-1199. doi: 10.1105/tpc.15.00725 https://archive-ouverte.unige.ch/unige:86423

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Deposited on : 2016-08-29

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