Organelle DNAs: The bit players in malaria parasite DNA replication

The replication mechanics of the extrachromosomal DNAs of the malaria parasite are beginning to be unravelled. At 6 kb, the mitochondrial genome is the smallest known and, unlike higher eukaryotes, its multiple copies per cell occur as polydisperse linear concatemers. Here, Don Williamson, Peter Preiser and Iain Wilson discuss recent evidence that this DNA replicates by a process akin to those of certain bacteriophages, which make use of extensive recombination coupled with rolling circles. The parasite's second extrachromosomal DNA, a 35 kb circular molecule thought to be a plastid remnant inherited from a remote photoautotroph, probably replicates in a more familiar fashion from conventional origins or D loops. Improved understanding of both organelle's replicative mechanisms could give new leads to malaria chemotherapy.