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Nat Plants. 2019 Jan;5(1):106-117. doi: 10.1038/s41477-018-0339-y. Epub 2019 Jan 9.

Small is big in Arabidopsis mitochondrial ribosome.

Author information

1
Institut de biologie de moléculaire des plantes UPR2357 du CNRS, Université de Strasbourg, Strasbourg, France.
2
Institut Jean-Pierre Bourgin INRA, AgroParisTech, CNRS, Université Paris-Saclay, Versailles, France.
3
Institut Européen de Chimie et Biologie U1212 Inserm, Université de Bordeaux, Pessac, France.
4
Plateforme protéomique Strasbourg Esplanade FRC1589 du CNRS, Université de Strasbourg, Strasbourg, France.
5
Institut Jean-Pierre Bourgin INRA, AgroParisTech, CNRS, Université Paris-Saclay, Versailles, France. hakim.mireau@inra.fr.
6
Institut Européen de Chimie et Biologie U1212 Inserm, Université de Bordeaux, Pessac, France. yaser.hashem@ubordeaux.fr.
7
Institut de biologie de moléculaire des plantes UPR2357 du CNRS, Université de Strasbourg, Strasbourg, France. giege@unistra.fr.

Abstract

Mitochondria are responsible for energy production through aerobic respiration, and represent the powerhouse of eukaryotic cells. Their metabolism and gene expression processes combine bacterial-like features and traits that evolved in eukaryotes. Among mitochondrial gene expression processes, translation remains the most elusive. In plants, while numerous pentatricopeptide repeat (PPR) proteins are involved in all steps of gene expression, their function in mitochondrial translation remains unclear. Here we present the biochemical characterization of Arabidopsis mitochondrial ribosomes and identify their protein subunit composition. Complementary biochemical approaches identified 19 plant-specific mitoribosome proteins, of which ten are PPR proteins. The knockout mutations of ribosomal PPR (rPPR) genes result in distinct macroscopic phenotypes, including lethality and severe growth delay. The molecular analysis of rppr1 mutants using ribosome profiling, as well as the analysis of mitochondrial protein levels, demonstrate rPPR1 to be a generic translation factor that is a novel function for PPR proteins. Finally, single-particle cryo-electron microscopy (cryo-EM) reveals the unique structural architecture of Arabidopsis mitoribosomes, characterized by a very large small ribosomal subunit, larger than the large subunit, bearing an additional RNA domain grafted onto the head. Overall, our results show that Arabidopsis mitoribosomes are substantially divergent from bacterial and other eukaryote mitoribosomes, in terms of both structure and protein content.

PMID:
30626926
DOI:
10.1038/s41477-018-0339-y
[Indexed for MEDLINE]

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