Endosymbiotic transfer of DNA from the cytoplasmic organelles (mitochondria and chloroplasts) to the nucleus has been a major factor driving the origin of new nuclear genes, a process central to eukaryote evolution. Typically, transfer of organelle DNA to the nucleus is quickly followed by decay, deletion and rearrangement. However, in rare instances these new sequences lead to functional relocation of organelle genes to the nucleus or the generation of genes with novel function. Similar transfer of chloroplast DNA has also added to the complexity of plant mitochondrial genomes. Significantly, these processes are ongoing, making promiscuous organellar DNA an important contributor to the continued evolution of plant genomes.