Overexpression of a diacylglycerol acyltransferase gene in Phaeodactylum tricornutum directs carbon towards lipid biosynthesis |
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| Authors: | Jorge Dinamarca Orly Levitan G. Kenchappa Kumaraswamy Desmond S. Lun Paul G. Falkowski |
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| Affiliation: | 1. Environmental Biophysics and Molecular Ecology Laboratory, Department of Marine and Coastal Sciences, Rutgers University, New Brunswick, New Jersey, USA;2. Environmental Biophysics and Molecular Ecology Laboratory, Departments of Marine and Coastal Sciences and Plant Biology and Pathology, Rutgers University, New Brunswick, New Jersey, USA;3. Waksman Institute and Department of Chemistry & Chemical Biology, Rutgers University, Piscataway, New Jersey, USA;4. Center for Computational and Integrative Biology and Department of Computer Science, Rutgers University, Camden, New Jersey, USA;5. Department of Plant Biology, Rutgers University, New Brunswick, New Jersey, USA;6. Environmental Biophysics and Molecular Ecology Laboratory, Departments of Marine and Coastal Sciences and Earth and Planetary Sciences, Rutgers University, Piscataway, New Jersey, USA |
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| 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 using 13C 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. |
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| Keywords: | carbon flux diatom lipids metabolic flux analysis metabolism |
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