Ribosome Assembly in plant MItochondria – RAMI

This project aims at understanding how ribosomes are assembled in plant mitochondria. Ribosomes are the main effectors of translation, the fundamental process, central to all cellular life, that converts genetic information into proteins. While translation has been well-studied in prokaryotes and eukaryotic cytosolic systems, mitochondrial translation is less understood. Mitochondria are the essential organelles of eukaryotic cells that generate ATP. They have their own genome and a complete gene expression machinery including a translation system. Recent studies have revealed the surprising diversity of mitochondrial translation systems across eukaryotes. In particular, mitoribosomes were found to be strikingly diverse in terms of compositions and structures. This level of structural variation is extraordinary, as it was never observed for any other types of ribosomes, i.e. bacterial or cytosolic. In particular, in plants, mitoribosomes have unique structural features, with plant-specific domains and contain several pentatricopeptide repeat proteins occurring as core ribosomal proteins. Nonetheless, most fundamental aspects of plant mitochondrial translation, in particular ribosome assembly, remain completely elusive. This project is expected to fill this gap by providing a comprehensive functional and mechanistic analysis of how the biogenesis of the mitochondrial translation apparatus is achieved in plants. Through a combination of complementary genetic, biochemical, and structural analyses, the research should reveal how rRNA modifications are established and how they impact mitoribosome assembly. It should identify the complete set of protein factors required for ribosome biogenesis and elucidate the sequence of events leading to the production of fully assembled mitoribosomes. This study will contribute to provide a comprehensive view of translation processes in plant mitochondria and help to determine the diversity of translation processes across eukaryotes.