2 . 10 Evolution of Organellar Genomes

In the plant kingdom, the endosymbiotic event of a mitochondrial ancestor probably happened first to plant cell progenitors followed by the endosymbiosis of a chloroplast ancestor, namely cyanobacteria. In this paper we describe the characterization of plant mitochondrial genome focussing on (I) the complexity of plant mitochondrial genomes, (2) the genetic codes utilized in plant mitochondrial genomes, (3) the properties of open reading frames encoded by introns (group I and group II) of plant mitochondrial genes, and (4) RNA editing which has been reported in wheat mitochondrial genome (C to U conversion), and (5) evolutionary events of gene migration from mitochondrial and chloroplast genomes to nuclear genomes.