Evolution of DNA sequence organization in mitochondrial genomes of Zea

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Abstract
Molecular mechanisms underlying the evolution of m[mitochondrial]DNA in maize and 3 spp. of teosinte were 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 4 spp. Of the cloned fragments, 1/3 showed sequences conserved in homology and position of BamHI restriction fragments. Other fragments produced patterns indicating that extensive rearrangement of DNA sequences occurred. In 2 cases, hybridization patterns revealed major changes in relative abundance of specific sequences that are probably 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.