Occurrence of nuclear-encoded tRNAIle in mitochondria of the liverwort Marchantia polymorpha

Abstract

 Although 29 tRNA genes have been deduced from the complete nucleotide sequence of the mitochondrial genome from the liverwort Marchantia polymorpha, a tRNA^Ile 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^Ile(AAU) gene from the liverwort. Northern analysis showed the presence of nuclear-encoded tRNA^Ile both in the mitochondrion and the cytosol, while both chloroplast DNA-encoded tRNA^Ile and nuclear-encoded tRNA^Tyr were absent in liverwort mitochondria. These results unequivocally establish that import of nuclear tRNA^Ile into mitochondria indeed occurs in one of the most primitive plants, M. polymorpha.