Microbiology and Molecular Biology Reviews, Mar 1997, 1-16, Vol 61, No. 1
RJ Wilson and DH Williamson
Malaria and related apicomplexan parasites have two highly conserved
organellar genomes: one is of plastid (pl) origin, and the other is
mitochondrial (mt). The organization of both organellar DNA molecules from
the human malaria parasite Plasmodium falciparum has been determined, and
they have been shown to be tightly packed with genes. The 35-kb circular
DNA is the smallest known vestigial plastid genome and is presumed to be
functional. All but two of its recognized genes are involved with genetic
expression: one of the two encodes a member of the clp family of molecular
chaperones, and the other encodes a conserved protein of unknown function
found both in algal plastids and in eubacterial genomes. The possible
evolutionary source and intracellular location of the plDNA are discussed.
The 6-kb tandemly repeated mt genome is the smallest known and codes for
only three proteins (cytochrome b and two subunits of cytochrome oxidase)
as well as two bizarrely fragmented rRNAs. The organization of the mt
genome differs somewhat among genera. The mtDNA sequence provides
information not otherwise available about the structure of apicomplexan
cytochrome b as well as the unusually fragmented rRNAs. The malarial mtDNA
has a phage-like replication mechanism and undergoes extensive
recombination like the mtDNA of some other lower eukaryotes.
Copyright © 1997, American Society for Microbiology
Extrachromosomal DNA in the Apicomplexa
National Institute for Medical Research, London, United Kingdom. r- wilson@nimr.mrc.ac.uk
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