The strange evolutionary history of plant mitochondrial tRNAs and their aminoacyl-tRNA synthetases

Abstract

The translation systems of plant mitochondria differ from those of other mitochondria in that they incorporate tRNAs of three different origins: native mitochondrial tRNAs, plastid tRNAs transcribed from plastid DNA insertions in mitochondrial DNA, and nuclearly encoded imported tRNAs. The complicated evolutionary history of the tRNA replacement events leading up to this situation is slowly being unraveled. Recent research on plant aminoacyl-tRNA synthetases is starting to reveal how the mitochondrial compartment can cope with this unusual mix of tRNAs and has uncovered an unprecedented degree of sharing of isoforms between compartments. Many plant aminoacyl-tRNA synthetases are dual targeted to two compartments, either cytosol/mitochondria or plastids/mitochondria. The molecular basis for some of these cases of dual targeting are described.