title: Overexpression of a diacylglycerol acyltransferase gene in Phaeodactylum tricornutum directs carbon towards lipid biosynthesis.
abstract: Under nutrient deplete conditions, diatoms accumulate between 15% to 25% of their dry weight as lipids, primarily as triacylglycerols (TAGs). As in most eukaryotes, these organisms produce TAGs via the acyl-CoA dependent Kennedy pathway. The last step in this pathway is catalyzed by diacylglycerol acyltransferase (DGAT) that acylates diacylglycerol (DAG) to produce TAG. To test our hypothesis that DGAT plays a major role in controlling the flux of carbon towards lipids, we overexpressed a specific type II DGAT gene, DGAT2D, in the model diatom Phaeodactylum tricornutum. The transformants had 50- to 100-fold higher DGAT2D mRNA levels and the abundance of the enzyme increased 30- to 50-fold. More important, these cells had a 2-fold higher total lipid content and incorporated carbon into lipids more efficiently than the wild type (WT) while growing only 15% slower at light saturation. Based on a flux analysis using13C as a tracer, we found that the increase in lipids was achieved via increased fluxes through pyruvate and acetyl-CoA. Our results reveal overexpression of DAGT2D increases the flux of photosynthetically fixed carbon towards lipids, and leads to a higher lipid content than exponentially grown WT cells.
authors.affiliation: Environmental Biophysics and Molecular Ecology Laboratory, Department of Marine and Coastal Sciences, Rutgers University, New Brunswick, New Jersey, 08901, USA.
authors.forename: Jorge
authors.initials: J
authors.lastname: Dinamarca
authors.affiliation: Environmental Biophysics and Molecular Ecology Laboratory, Departments of Marine and Coastal Sciences and Plant Biology and Pathology, Rutgers University, New Brunswick, New Jersey, 08901, USA.
authors.forename: Orly
authors.initials: O
authors.lastname: Levitan
authors.affiliation: Waksman Institute and Department of Chemistry & Chemical Biology, Rutgers University, Piscataway, New Jersey, 08854, USA.
authors.forename: G Kenchappa
authors.initials: GK
authors.lastname: Kumaraswamy
authors.affiliation: Center for Computational and Integrative Biology and Department of Computer Science, Rutgers University, Camden, New Jersey, 08102, USA.|Department of Plant Biology, Rutgers University, New Brunswick, New Jersey, 08901, USA.
authors.forename: Desmond S
authors.initials: DS
authors.lastname: Lun
authors.affiliation: Environmental Biophysics and Molecular Ecology Laboratory, Departments of Marine and Coastal Sciences and Earth and Planetary Sciences, Rutgers University, Piscataway, New Jersey, 0885, USA.
authors.forename: Paul G
authors.initials: PG
authors.lastname: Falkowski
mesh_terms: D002244:Carbon / Q000378:metabolism*; D051048:Diacylglycerol O-Acyltransferase / Q000378:metabolism*; D017377:Diatoms / Q000378:metabolism*; D004075:Diglycerides / Q000378:metabolism; D050356:Lipid Metabolism / Q000502:physiology; D010788:Photosynthesis / Q000502:physiology; D014280:Triglycerides / Q000378:metabolism
chemical_list: C011439:1,2-diacylglycerol; D004075:Diglycerides; D014280:Triglycerides; D002244:Carbon; D051048:Diacylglycerol O-Acyltransferase
keywords: carbon flux; diatom; lipids; metabolic flux analysis; metabolism