The T-domain of cytosolic tRNAVal, an essential determinant for mitochondrial import

Import of tRNAs into plant mitochondria appears to be highly specific. We recently showed that the anticodon and the D-domain sequences are essential determinants for tRNAVal import into tobacco cell mitochondria. To determine the minimal set of elements required to direct import of a cytosol-specific tRNA species, tobacco cells were transformed with an Arabidopsis thaliana intron-containing tRNAMet-e gene carrying the D-domain and the anticodon of a valine tRNA. Although well expressed and processed into tobacco cells, this mutated tRNA was shown to remain in the cytosol. Furthermore, a mutant tRNAVal carrying the T-domain of the tRNAMet-e, although still efficiently recognized by the valyl-tRNA synthetase, is not imported into mitochondria. Altogether these results suggest that mutations affecting the core of a tRNA molecule also alter its import ability into plant mitochondria.