Steady-state levels of imported tRNAs in Chlamydomonas mitochondria are correlated with both cytosolic and mitochondrial codon usages.
The mitochondrial genome of Chlamydomonas reinhardtii only encodes three expressed tRNA genes, thus most mitochondrial tRNAs are likely imported. The sharing of tRNAs between chloroplasts and mitochondria has been speculated in this organism. We first demonstrate that no plastidial tRNA is present in mitochondria and that the mitochondrial translation mainly relies on the import of nucleus-encoded tRNA species. Then, using northern analysis, we show that the extent of mitochondrial localization for the 49 tRNA isoacceptor families encoded by the C. reinhardtii nuclear genome is highly variable. Until now the reasons for such variability were unknown. By comparing cytosolic and mitochondrial codon usage with the sub-cellular distribution of tRNAs, we provide unprecedented evidence that the steady-state level of a mitochondrial tRNA is linked not only to the frequency of the cognate codon in mitochondria but also to its frequency in the cytosol, then allowing optimal mitochondrial translation.
Vinogradova
Elizaveta
E
Institut de Biologie Moléculaire des Plantes, Unité Propre de Recherche 2357, Université Louis Pasteur, Centre National de la Recherche Scientifique, 12 rue du Général Zimmer, 67084 Strasbourg Cedex, France.
Salinas
Thalia
T
Cognat
Valérie
V
Remacle
Claire
C
Maréchal-Drouard
Laurence
L
D000818:Animals; D016825:Chlamydomonas reinhardtii / Q000235:genetics* / Q000378:metabolism; D003062:Codon; D003600:Cytosol / Q000378:metabolism; D054629:Genome, Mitochondrial; D008928:Mitochondria / Q000235:genetics* / Q000378:metabolism; D018087:Plastids / Q000235:genetics; D012313:RNA / Q000235:genetics / Q000378:metabolism; D034443:RNA Transport; D000077278:RNA, Mitochondrial; D012343:RNA, Transfer / Q000235:genetics / Q000378:metabolism*
D003062:Codon; D000077278:RNA, Mitochondrial; D012313:RNA; D012343:RNA, Transfer