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Many parasitic Apicomplexa, such as Plasmodium falciparum, contain an unpigmented chloroplast remnant termed the apicoplast, which is a target for malaria treatment. However, no close relative of apicomplexans with a functional photosynthetic plastid has yet been described. Here we describe a newly cultured organism that has ultrastructural features typical for alveolates, is phylogenetically related to apicomplexans, and contains a photosynthetic plastid. The plastid is surrounded by four membranes, is pigmented by chlorophyll a, and uses the codon UGA to encode tryptophan in the psbA gene. This genetic feature has been found only in coccidian apicoplasts and various mitochondria. The UGA-Trp codon and phylogenies of plastid and nuclear ribosomal RNA genes indicate that the organism is the closest known photosynthetic relative to apicomplexan parasites and that its plastid shares an origin with the apicoplasts. The discovery of this organism provides a powerful model with which to study the evolution of parasitism in Apicomplexa.

Item Type:	Refereed Article
Research Division:	Biological Sciences
Research Group:	Evolutionary biology
Research Field:	Phylogeny and comparative analysis
Objective Division:	Expanding Knowledge
Objective Group:	Expanding knowledge
Objective Field:	Expanding knowledge in the environmental sciences
UTAS Author:	Davies, NW (Associate Professor Noel Davies)
UTAS Author:	Bolch, CJS (Associate Professor Christopher Bolch)
ID Code:	50351
Year Published:	2008
Web of Science® Times Cited:	315
Deposited By:	Central Science Laboratory
Deposited On:	2008-07-31
Last Modified:	2009-11-11
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