Presence and absence of large inverted repeats in the mitochondrial DNA of Hyphochytriomycetes

Abstract

Physical maps of the mitochondrial DNA (mtDNA) of Hyphochytrium catenoides and Rhizidiomyces apophysatus were constructed. Hyphochytrium catenoides has a 54-kb (kilobase pair) circular mtDNA with an inverted repeat of 13.5–14.5 kb which contains the large ribosomal RNA gene at one extreme of the inverted repeat, adjacent to the small unique region. Genome complexity (genome size minus one arm of the inverted repeat) is 39.5–40.5 kb, identical with the average value for Oomycetes. Rhizidiomyces apophysatus has a 50-kb circular mtDNA with no inverted repeat. No obvious alignment of the two maps is possible. The occurrence of a typical inverted repeat in a group of fungi closely related to the Oomycetes indicates that the character is ancestral for the Oomycetes and that its modification or loss within the Oomycetes can be treated as a derived character for the purpose of phylogenetic analysis.