Genic rearrangements in Phytophthora mitochondrial DNA.

To assess evolutionary relationships among the oomycetous fungi we have constructed a physical and genic map of the mtDNA of a broad host range strain (695T) of Phytophthora megasperma. While, like other Phytophthora species, this 43.5 kb circular genome lacks the typical oomycete large inverted repeat, a short 0.5-0.9 kb inverted repeat has been identified. Comparison of the relative order of seven genic regions with host-specific Phytophthora strains reveals both a clustering of these loci within one-third of the host-specific genomes, and two genic inversions relative to the broad host range genome. The location of the short inverted repeat suggests that at least one of the inversions is a consequence of intramolecular recombination between repeat elements.