| The nucleotide sequence of the mitochondrially encoded cox2 (cytochrome c oxidase subunit 2) has been used to develop a molecular phylogeny for the Oomycota. Restriction fragments containing all of the cox2 coding region, or PCR fragments of an internal region of cox2, were cloned from 15 oomycete genera representing four major orders. A similar region from the hyphochytriomycete Hyphochytrium catenoides was also cloned for use as an outgroup. Analyses using maximum parsimony, neighbor-joining, and maximum likelihood of a common 622-631 nucleotide region and its deduced amino acid sequence is presented. Monophyletic groups have been hypothesized at the ordinal level for the Saprolegniales, Leptomitales, and Pythiales. At the amino acid level a tripeptide sequence was absent from all representatives of the Saprolegniales, but present in all examined representatives of the other three orders and H. catenoides. These analyses also suggest a closer affinity of the Leptomitales with the Saprolegniales rather than the Rhipidales. Similarly, the Rhipidales are more closely associated with the Pythiales. |
