Import and editing of plant mitochondrial transfer RNAs

The recombinations and mutations that higher plant mitochondrial (mt) DNA has undergone during evolution have led to the inactivation or complete loss of a number of the native transfer RNA (tRNA) genes deriving from the genome of the ancestral endosymbiont. Whereas the mt genome of the bryophyte Marchantia polymorpha still contains almost all these native tRNA genes (Oda et al. 1992a and b), one third to one half of them have disappeared from higher plant mitochondria and the remaining genes cannot provide for the needs of the mt translation system (Ceci et al. 1996, Sangare et al. 1990, Unseld et al. 1997, Weber-Lotfi et al. 1993).