Evolution of DNA sequence organization in mitochondrial genomes of Zea.

Molecular mechanisms underlying the evolution of mtDNA in maize and three species of teosinte have been investigated. By using DNA transfer techniques and cloned fragments of maize mtDNA, changes in the position of homologous sequences in restriction digests were analyzed in related taxa. The resulting patterns indicate general conservation of sequence homology in all four species. One-third of the cloned fragments showed sequences conserved in homology and position of BamHI restriction fragments. Other fragments produced patterns indicating that extensive rearrangement of DNA sequences has taken place. In two cases, hybridization patterns revealed major changes in relative abundance of specific sequences that we believe are related to the molecular heterogeneity phenomenon of maize mtDNA. The evolution of mtDNA in these plants appears dramatically different from that in animal mtDNA, where base substitutions may account for most of the observed changes in restriction patterns.