EVOLUTION OF MITOCHONDRIAL GENOMES IN FUNGI

This chapter describes sizes, gene topology, and structures contributing to size variation of mitochondrial DNA (mtDNAs) in fungi. It also presents mechanisms for generating length mutations and rearrangements together with a description of mtDNA codon variations. Two unusual features of mtDNA from oomycetes and hypochytridiomycetes groups include (1) the circular mtDNA in Achyla ambisexualis has inverted repeats, and (2) genome complexity—namely, single copy length, falls in a narrow range between 36.2 kb and 45.3 kb. Macro structural changes to fungal mtDNAs can involve length mutations and rearrangements. A micro structural change can lead to variation to the genetic code both between different groups of fungi and in relation to other organisms. Intron loss from mitochondrial genomes can be achieved experimentally and the mechanism is thought to proceed by an RNA intermediate and reverse transcription. Intron polymorphisms may produce subtle changes allowing organisms to exploit different niches. Loss of intergenic regions may occur through recombination–excision processes or, for small regions, by slipped-strand mispairing. © 1992, Academic Press Inc.