DNA sequence analysis of the 24.5 kilobase pair cytochrome oxidase subunit I mitochondrial gene from Podospora anserina: a gene with sixteen introns.

The DNA sequence of a 26.7 Kilobase pair (10(3) base pairs = 1 Kb) region of the mitochondrial genomes of races s and A from Podospora anserina was determined. Within this region, the 24.5 Kb cytochrome oxidase subunit I gene was located and its exon sequences determined by computer analysis comparisons with other fungal genes. The Podospora COI gene was interrupted by two group II introns (one in race s) and fourteen group I introns ranging in size from about 2.2 Kb to 404 bp. Earlier studies on secondary structure analysis, as well as comparison of their open reading frames (ORFs), showed that the two group II introns were closely related. The fourteen group I introns were representatives of three subgroupings (IB, C and a new category, subgroup ID). Two of these group I introns were separated by just a single exon codon. The analysis of all these introns is discussed in comparison with other fungal introns as well as with the known Podospora anserina introns.