Expression of Arabidopsis thaliana mitochondrial alanyl-tRNA synthetase is not sufficient to trigger mitochondrial import of tRNAAla in yeast.
It has often been suggested that precursors to mitochondrial aminoacyl-tRNA synthetases are likely carriers for mitochondrial import of tRNAs in those organisms where this process occurs. In plants, it has been shown that mutation of U(70) to C(70) in Arabidopsis thaliana tRNA(Ala)(UGC) blocks aminoacylation and also prevents import of the tRNA into mitochondria. This suggests that interaction of tRNA(Ala) with alanyl-tRNA synthetase (AlaRS) is necessary for import to occur. To test whether this interaction is sufficient to drive import, we co-expressed A. thaliana tRNA(Ala)(UGC) and the precursor to the A. thaliana mitochondrial AlaRS in Saccharomyces cerevisiae. The A. thaliana enzyme and its cognate tRNA were correctly expressed in yeast in vivo. However, although the plant AlaRS was efficiently imported into mitochondria in the transformed strains, we found no evidence for import of the A. thaliana tRNA(Ala) nor of the endogenous cytosolic tRNA(Ala) isoacceptors. We conclude that at least one other factor besides the mitochondrial AlaRS precursor must be involved in mitochondrial import of tRNA(Ala) in plants.
Mireau
H
H
Station de Génétique et d'Amélioration des Plantes, Institut National de la Recherche Agronomique, Route de St.-Cyr, F-78026 Versailles Cedex, France. mireau@versailles.inra.fr
Cosset
A
A
Marechal-Drouard
L
L
Fox
T D
TD
Small
I D
ID
Dietrich
A
A
D000412:Alanine-tRNA Ligase / Q000096:biosynthesis* / Q000235:genetics; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics; D001692:Biological Transport; D015966:Gene Expression Regulation, Fungal; D018014:Gene Transfer Techniques; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism*; D012346:RNA, Transfer, Amino Acyl / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae
D012346:RNA, Transfer, Amino Acyl; D000412:Alanine-tRNA Ligase