title: The evolutionary origin of the 35 kb circular DNA of Plasmodium falciparum: new evidence supports a possible rhodophyte ancestry.
abstract: In common with other Apicomplexan parasites, Plasmodium falciparum carries two extrachromosomal DNAs, one of which, the 6 kb element, is undoubtedly mitochondrial. The second, generally referred to as the 35 kb circle, is of unknown provenance, but the nature and organization of its genetic content makes a mitochondrial association unlikely and the molecule has features reminiscent of plastid genomes. We now report the occurrence on the circle of an open reading frame specifying a predicted 470 amino acid protein that shares more than 50% identity with a gene currently known only on the plastome of red algae. This high degree of conservation confirms the 35 kb circle's plastid ancestry, and we speculate that it may have originated from the rhodoplast of an ancient red algal endosymbiont in the progenitor of the Apicomplexa.
authors.affiliation: National Institute for Medical Research, The Ridgeway, Mill Hill, London, UK.
authors.forename: D H
authors.initials: DH
authors.lastname: Williamson
authors.forename: M J
authors.initials: MJ
authors.lastname: Gardner
authors.forename: P
authors.initials: P
authors.lastname: Preiser
authors.forename: D J
authors.initials: DJ
authors.lastname: Moore
authors.forename: K
authors.initials: K
authors.lastname: Rangachari
authors.forename: R J
authors.initials: RJ
authors.lastname: Wilson
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D016384:Consensus Sequence; D004270:DNA, Circular / Q000235:genetics*; D016054:DNA, Protozoan / Q000235:genetics; D005111:Extrachromosomal Inheritance / Q000235:genetics; D017343:Genes, Plant / Q000235:genetics; D017125:Genes, Protozoan / Q000235:genetics*; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics; D010963:Plasmodium falciparum / Q000235:genetics*; D018087:Plastids; D000461:Rhodophyta / Q000235:genetics*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid
chemical_list: D004270:DNA, Circular; D016054:DNA, Protozoan; D010940:Plant Proteins