Translational control by PPR proteins in plant mitochondria

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Tan, Trung | Ngom, Talla | Wang, Chuande | Quadrado, Martine | Dargel-Graffin, Céline | Namy, Olivier | Mireau, Hakim

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International audience. The control of translation in plant mitochondria is still not understood at the molecular level. A growing body of evidence indicates though that mitochondrial translation differs from its bacterial counterpart in many key aspects. Moreover, recent cryo-EM structural analyses have revealed highly divergent composition and structures of mitoribosomes in eukaryotes, suggesting specific adaptations of the translational apparatus between fila that may notably impact translation initiation. Our recent analysis of plant translatomes by ribosome profiling analysis revealed highly variable ribosome loads per mitochondrial mRNA, suggesting tight control of translation initiation or elongation in plant mitochondria (Planchard et al, 2018). Furthermore, downstream orfs of di-citronic transcripts have higher ribosomal loads than their upstream cognate orfs, clearly indicating an ability of plant ribosomes to initiate translation internally in mRNAs. To better understand the basis of this control, we have identified and characterized mitochondria-targeted pentatricopeptide repeat (PPR) proteins specifically involved in translation. I will present our most recent advances on the characterization of these PPR proteins.Planchard, N., Bertin, P., Quadrado, M., Dargel-Graffin, C., Hatin, I., Namy, O. and Mireau, H. (2018) The translational landscape of Arabidopsis mitochondria. Nucleic Acids Res., 283, 1476.

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