Fungal Mitochondrial Genomes

Comparison of mitochondrial genomes among eukaryotic organisms reveals large size differences between animal, fungal, protist and plant species. The average size of animal mtDNA is approximately 16 kb (Boore 1999), whereas plant mtDNAs range from 200 to 2500 kb—larger than some prokaryotic genomes (Palmer 1990). The size of fungal mtDNAs fall between the average animal and lower limit of plant mtDNAs, ranging from 19 kb to 176 kb (Hudspeth 1992). Despite the nearly 10-fold difference in size, there is not a corresponding difference in the number or types of genes encoded by fungal mtDNAs. Most fungal genomes encode the same set of 14 polypeptides, all of which are hydrophobic components of the respiratory chain (see Homepage ), as well as a minimal set of tRNAs and rRNAs necessary for their translation (see Table 1). A few additional genes are found in some genomes and many contain several unidentified open reading frames (ORFs). A list of genes and mutants in Neurospora crassa can be found in Table 2. Non-coding regions are usually comprised of AT-rich and repeated sequences as well as introns. Fungal and plant mitochondria also can harbor extrachromosomal DNA plasmids and/or double-stranded RNAs (see Mt Plasmids). >

REFERENCES