Lawrence Berkeley National Laboratory

The complete sequences of the mitochondrial genomes of the oomycetes of Phytophthora ramorum and P. sojae were determined during the course of their complete nuclear genome sequencing (Tyler, et al. 2006). Both are circular, with sizes of 39,314 bp for P. ramorum and 42,975 bp for P. sojae. Each contains a total of 37 identifiable protein-encoding genes, 25 or 26 tRNAs (P. sojae and P. ramorum, respectively) specifying 19 amino acids, and a variable number of ORFs (7 for P. ramorum and 12 for P. sojae) which are potentially additional functional genes. Non-coding regions comprise approximately 11.5 percent and 18.4 percent of the genomes of P. ramorum and P. sojae, respectively. Relative to P. sojae, there is an inverted repeat of 1,150 bp in P. ramorum that includes an unassigned unique ORF, a tRNA gene, and adjacent non-coding sequences, but otherwise the gene order in both species is identical. Comparisons of these genomes with published sequences of the P. infestans mitochondrial genome reveals a number of similarities, but the gene order in P. infestans differs in two adjacent locations due to inversions. Sequence alignments of the three genomes indicated sequence conservation ranging from 75 to 85 percent and that specific regions were more variable than others.