Occurrence of nuclear-encoded tRNA(IIe) in mitochondria of the liverwort Marchantia polymorpha

Although 29 tRNA genes have been deduced from the complete nucleotide sequence of the mitochondrial genome from the liverwort Marchantia polymorpha, a tRNA(IIe) gene decoding AUU and AUC codons is conspicuously absent. In order to address the question of the possible involvement of nuclear-encoded tRNA, we isolated and identified three variant copies of the nuclear-encoded tRNA(IIe)(AAU) gene from the liverwort. Northern analysis showed the presence of nuclear-encoded tRNA(IIe) both in the mitochondrion and the cytosol, while both chloroplast DNA-encoded tRNA(IIe) and nuclear-encoded tRNA(Tyr) were absent in liverwort mitochondria. These results unequivocally establish that import of nuclear tRNAT(IIe) into mitochondria indeed occurs in one of the most primitive plants. M. polymorpha.