EVOLUTION OF A MITOCHONDRIAL TRANSFER-RNA PHE GENE IN A-THALIANA - IMPORT OF CYTOSOLIC TRANSFER-RNA PHE INTO MITOCHONDRIA

Previously we have described a putative tRNA(Tyr) in Arabidopsis thali ana mitochondria, the sequence of which is different from that of othe r plant mitochondrial tRNA(Tyr) genes. We show here that this tRNA(Tyr ) gene sequence is present in several copies in the mitochondrial geno me of A. thaliana. One copy of these tRNA(Tyr) gene sequences, termed here tRNA(Tyr-1), could encode a functional tRNA. Expression analysis has shown that the tRNA(Tyr-1) gene is cotranscribed with the downstre am tRNA(Glu) gene, and that the corresponding mature-sized tRNA is pre sent in mitochondria. We also show that the native tRNA(Tyr) gene, sim ilar to the mitochondrial tRNA(Tyr) genes found in plants, is present in the A. thaliana mitochondrial genome and expressed. The tRNA(Tyr-1) gene has been previously suggested to be derived from a tRNA(Phe) gen e sequence. We show here that, as a consequence, there is no tRNA(Phe) gene in the mitochondrial genome of A. thaliana and that a cytosolic tRNA(Phe) is imported in A. thaliana mitochondria. (C) 1997 Academic P ress.