Analysis of the translational landscape of Arabidopsis mitochondria

Messenger RNA translation is a complex process that is still poorly understood in eukaryotic organelles like mitochondria. Growing evidence indicate though that mitochondrial translation differs from its bacterial counterpart in many key aspects. In this analysis, we used the ribosome profiling technology to generate a genome-wide snapshot view of mitochondrial translation in Arabidopsis. We show that, unlike in humans, most Arabidopsis mitochondrial ribosomes footprints measure 27 and 28 bases. We also reveal that respiratory subunits encoding mRNAs show much higher ribosome association than other mitochondrial mRNAs, implying that they are translated to higher levels. Homogenous ribosome densities were generally detected within each respiratory complex except for complex V where higher ribosome coverage corroborate with higher needs in specific subunits. In complex I respiratory mutants, a slight reorganization of mitochondrial mRNAs ribosome association was detected involving an increase in ribosome densities on certain ribosomal protein encoding transcripts and a reduction in the translation of a few complex V mRNAs. Altogether, our observations reveal that plant mitochondrial translation is a dynamic process and that translational control is important for gene expression in plant mitochondria. This study paves the way for future advances in the understanding of translation in higher plant mitochondria. Overall design: In this study, 2 Arabidopsis mutants are compared to the wild type using duplicates for the Ribosome Profiling experiment. RNASEQ: was conducted to observe the editing rates of Col0 transcripts. RIBOSEQ: was conducted to observe the ribosome occupancy on each transcript of wild type and mutants.

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Planchard N, Bertin P, Quadrado M, Dargel-Graffin C, Hatin I, Namy O, Mireau H