Comparative analysis of Fusarium mitochondrial genomes reveals a highly variable region that encodes an exceptionally large open reading frame

► First comparative genomic analysis of Fusarium mitochondrial DNAs. ► Discovery of a horizontally transmitted region that encodes a large, unidentified ORF. ► Identification of two additional mitochondrial ORFs that are under positive selection. ► Evidence that 3′ gene duplication can modify genes and create new ORFs.