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Functional diversity of ribosomal proteins in plant mitochondria
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Edité par CCSD -
International audience. The expression of mitochondrial genes implies a tight cooperation between degenerated prokaryotic-like features and nuclear-encoded eukaryotic-derived factors that appeared throughout the evolution. This dual origin has resulted in complex mRNA expression processes that are still poorly understood at the molecular level. This is particularly true for mitochondrial translation, which has remained largely unexplored notably in higher plants. Yet, we know that the mitochondrial translation machinery differs profoundly from its bacterial counterpart in many essential aspects. To better understand the functioning of the plant mitochondrial machinery, we classified and analysed nuclear genes encoding potential mitochondria-targeted ribosomal proteins in Arabidopsis thaliana. This exhaustive survey led to us to observe that most ribosomal and ribosomal-like proteins are encoded in small gene families comprising up to 10 members. Further analyses suggested that several of such families may not correspond to multigene families sensus stricto. To explore the activity and the functional diversification of ribosomal proteins in plants, we selected and analysed in details several of the identified families. The sub-cellular distribution of selected proteins was determined by GFP fusion and Arabidopsis mutants affected in the corresponding genes were characterized at the molecular level. Very interestingly, our results revealed several cases of molecular exaptation and the acquisition of extra-ribosomal functions in organellar mRNA expression for certain ribosomal-like proteins. Our results clearly demonstrated that ribosomal protein genes can diversify functionally and acquire functions outside of the ribosome to regulate gene expression.
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