Mitochondrial genomes: anything goes

Mitochondrial genomes: anything goes

http://www.cell.com/trends/genetics/abstract/S0168-9525%2803%2900304-4

This is a really nice review of the crazy diversity in physical and genetic structure of mitochondrial genomes throughout eukaryotes. Because, in the early days, research focussed on animals, it was a while before this diversity became apparent. For example, it was thought that all mtDNA molecules were circular, and mapped circularly; there's now evidence for mtDNAs that map circularly but consist of many linearly concatenated sections, and mtDNAs that map linearly, and even some with multiple "chromosomes".

There's great diversity in mtDNA length and gene content, and not an obvious correlation between the two. Plasmodium parasites have mtDNA about 6 kbp long; rice's is 490 kbp (plant mtDNA in general is a bit crazy). Individual mitochondrial genes are often highly noncontiguous, broken up into many pieces that are jumbled and may lie on either strand of the mtDNA. Some interesting hypotheses are raised as to the reasons for this diversity, including horizontal transfer of mitochondrial genes, the special case of parasitism, and "competence" of plant mtDNA whereby genetic information from chloroplasts, nuclear, viral, and as-yet-unknown sources has been assimilated. Well worth a read!