title: Identification of plant-like galactolipids in Chromera velia, a photosynthetic relative of malaria parasites.
abstract: Apicomplexa are protist parasites that include Plasmodium spp., the causative agents of malaria, and Toxoplasma gondii, responsible for toxoplasmosis. Most Apicomplexa possess a relict plastid, the apicoplast, which was acquired by secondary endosymbiosis of a red alga. Despite being nonphotosynthetic, the apicoplast is otherwise metabolically similar to algal and plant plastids and is essential for parasite survival. Previous studies of Toxoplasma gondii identified membrane lipids with some structural features of plastid galactolipids, the major plastid lipid class. However, direct evidence for the plant-like enzymes responsible for galactolipid synthesis in Apicomplexan parasites has not been obtained. Chromera velia is an Apicomplexan relative recently discovered in Australian corals. C. velia retains a photosynthetic plastid, providing a unique model to study the evolution of the apicoplast. Here, we report the unambiguous presence of plant-like monogalactosyldiacylglycerol and digalactosyldiacylglycerol in C. velia and localize digalactosyldiacylglycerol to the plastid. We also provide evidence for a plant-like biosynthesis pathway and identify candidate galactosyltranferases responsible for galactolipid synthesis. Our study provides new insights in the evolution of these important enzymes in plastid-containing eukaryotes and will help reconstruct the evolution of glycerolipid metabolism in important parasites such as Plasmodium and Toxoplasma.
authors.affiliation: School of Botany, University of Melbourne, Parkville, Victoria, Australia.
authors.forename: Cyrille Y
authors.initials: CY
authors.lastname: Botté
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Yamaryo-Botté
authors.forename: Jan
authors.initials: J
authors.lastname: Janouskovec
authors.forename: Thusita
authors.initials: T
authors.lastname: Rupasinghe
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Keeling
authors.forename: Paul
authors.initials: P
authors.lastname: Crellin
authors.forename: Ross L
authors.initials: RL
authors.lastname: Coppel
authors.forename: Eric
authors.initials: E
authors.lastname: Maréchal
authors.forename: Malcolm J
authors.initials: MJ
authors.lastname: McConville
authors.forename: Geoffrey I
authors.initials: GI
authors.lastname: McFadden
mesh_terms: D000595:Amino Acid Sequence; D016782:Apicomplexa / Q000235:genetics / Q000378:metabolism*; D019143:Evolution, Molecular; D038983:Galactolipids / Q000096:biosynthesis* / Q000235:genetics; D008954:Models, Biological; D008969:Molecular Sequence Data; D018087:Plastids / Q000235:genetics / Q000378:metabolism*; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D038983:Galactolipids; D015800:Protozoan Proteins