title: Tracking the sterol biosynthesis pathway of the diatom Phaeodactylum tricornutum.
abstract: Diatoms are unicellular photosynthetic microalgae that play a major role in global primary production and aquatic biogeochemical cycling. Endosymbiotic events and recurrent gene transfers uniquely shaped the genome of diatoms, which contains features from several domains of life. The biosynthesis pathways of sterols, essential compounds in all eukaryotic cells, and many of the enzymes involved are evolutionarily conserved in eukaryotes. Although well characterized in most eukaryotes, the pathway leading to sterol biosynthesis in diatoms has remained hitherto unidentified. Through the DiatomCyc database we reconstructed the mevalonate and sterol biosynthetic pathways of the model diatom Phaeodactylum tricornutum in silico. We experimentally verified the predicted pathways using enzyme inhibitor, gene silencing and heterologous gene expression approaches. Our analysis revealed a peculiar, chimeric organization of the diatom sterol biosynthesis pathway, which possesses features of both plant and fungal pathways. Strikingly, it lacks a conventional squalene epoxidase and utilizes an extended oxidosqualene cyclase and a multifunctional isopentenyl diphosphate isomerase/squalene synthase enzyme. The reconstruction of the P. tricornutum sterol pathway underscores the metabolic plasticity of diatoms and offers important insights for the engineering of diatoms for sustainable production of biofuels and high-value chemicals.
authors.affiliation: Department of Plant Systems Biology, VIB, Technologiepark 927, B-9052, Gent, Belgium.|Department of Plant Biotechnology and Bioinformatics, Ghent University, Technologiepark 927, B-9052, Gent, Belgium.|Department of Biology, Laboratory of Protistology and Aquatic Ecology, Ghent University, Krijgslaan 281 (S8), B-9000, Gent, Belgium.
authors.forename: Michele
authors.initials: M
authors.lastname: Fabris
authors.affiliation: Department of Plant Systems Biology, VIB, Technologiepark 927, B-9052, Gent, Belgium.|Department of Plant Biotechnology and Bioinformatics, Ghent University, Technologiepark 927, B-9052, Gent, Belgium.|Department of Biology, Laboratory of Protistology and Aquatic Ecology, Ghent University, Krijgslaan 281 (S8), B-9000, Gent, Belgium.
authors.forename: Michiel
authors.initials: M
authors.lastname: Matthijs
authors.affiliation: Department of Plant Systems Biology, VIB, Technologiepark 927, B-9052, Gent, Belgium.|Department of Plant Biotechnology and Bioinformatics, Ghent University, Technologiepark 927, B-9052, Gent, Belgium.
authors.forename: Sophie
authors.initials: S
authors.lastname: Carbonelle
authors.affiliation: Department of Plant Systems Biology, VIB, Technologiepark 927, B-9052, Gent, Belgium.|Department of Plant Biotechnology and Bioinformatics, Ghent University, Technologiepark 927, B-9052, Gent, Belgium.
authors.forename: Tessa
authors.initials: T
authors.lastname: Moses
authors.affiliation: Department of Plant Systems Biology, VIB, Technologiepark 927, B-9052, Gent, Belgium.|Department of Plant Biotechnology and Bioinformatics, Ghent University, Technologiepark 927, B-9052, Gent, Belgium.
authors.forename: Jacob
authors.initials: J
authors.lastname: Pollier
authors.affiliation: Department of Biology, Laboratory of Protistology and Aquatic Ecology, Ghent University, Krijgslaan 281 (S8), B-9000, Gent, Belgium.
authors.forename: Renaat
authors.initials: R
authors.lastname: Dasseville
authors.affiliation: Department of Plant Systems Biology, VIB, Technologiepark 927, B-9052, Gent, Belgium.|Department of Plant Biotechnology and Bioinformatics, Ghent University, Technologiepark 927, B-9052, Gent, Belgium.|Department of Biology, Laboratory of Protistology and Aquatic Ecology, Ghent University, Krijgslaan 281 (S8), B-9000, Gent, Belgium.
authors.forename: Gino J E
authors.initials: GJE
authors.lastname: Baart
authors.affiliation: Department of Biology, Laboratory of Protistology and Aquatic Ecology, Ghent University, Krijgslaan 281 (S8), B-9000, Gent, Belgium.
authors.forename: Wim
authors.initials: W
authors.lastname: Vyverman
authors.affiliation: Department of Plant Systems Biology, VIB, Technologiepark 927, B-9052, Gent, Belgium.|Department of Plant Biotechnology and Bioinformatics, Ghent University, Technologiepark 927, B-9052, Gent, Belgium.
authors.forename: Alain
authors.initials: A
authors.lastname: Goossens
mesh_terms: D003198:Computer Simulation; D017377:Diatoms / Q000378:metabolism*; D004926:Escherichia coli; D005786:Gene Expression Regulation / Q000502:physiology; D008798:Mevalonic Acid / Q000737:chemistry / Q000378:metabolism*; D008954:Models, Biological; D015394:Molecular Structure; D012441:Saccharomyces cerevisiae; D013261:Sterols / Q000737:chemistry / Q000378:metabolism*
chemical_list: D013261:Sterols; D008798:Mevalonic Acid
keywords: Phaeodactylum tricornutum; chimeric pathway; diatom; fusion enzymes; isopentenyl diphosphate isomerase; oxidosqualene cyclase; squalene epoxidase; sterol biosynthesis