DNA transposition between plant organellar genomes

Higher plant mitochondrial and chloroplast DNAs are known to share extensive sequence homologies. The present work addresses issues raised by these initial observations: (1) what is the distributive pattern of ctDNA sequences among different mitochondrial genomes, (2) what is the frequency of DNA transposition between the two organelles, (3) are the transposed ctDNA sequences transcribed? The results to be presented demonstrate that many ctDNA sequences, including identified genes, are widespread in mitochondrial genomes and in some cases are highly conserved. However, the distribution of any one particular sequence is sporadic, even within a plant family. Preliminary data, obtained in studies of watermelon, raise the possibility that some mtDNA transcripts share homology with ctDNA sequences.