title: Metabolome Analysis Reveals Betaine Lipids as Major Source for Triglyceride Formation, and the Accumulation of Sedoheptulose during Nitrogen-Starvation of Phaeodactylum tricornutum.
abstract: Oleaginous microalgae are considered as a promising resource for the production of biofuels. Especially diatoms arouse interest as biofuel producers since they are most productive in carbon fixation and very flexible to environmental changes in the nature. Naturally, triacylglycerol (TAG) accumulation in algae only occurs under stress conditions like nitrogen-limitation. We focused on Phaeodactylum strain Pt4 (UTEX 646), because of its ability to grow in medium with low salinity and therefore being suited when saline water is less available or for wastewater cultivation strategies. Our data show an increase in neutral lipids during nitrogen-depletion and predominantly 16:0 and 16:1(n-7) accumulated in the TAG fraction. The molecular species composition of TAG suggests a remodeling primarily from the betaine lipid diacylglyceroltrimethylhomoserine (DGTS), but a contribution of the chloroplast galactolipid monogalactosyldiacylglycerol (MGDG) cannot be excluded. Interestingly, the acyl-CoA pool is rich in 20:5(n-3) and 22:6(n-3) in all analyzed conditions, but these fatty acids are almost excluded from TAG. Other metabolites most obviously depleted under nitrogen-starvation were amino acids, lyso-phospholipids and tricarboxylic acid (TCA) cycle intermediates, whereas sulfur-containing metabolites as dimethylsulfoniopropionate, dimethylsulfoniobutyrate and methylsulfate as well as short acyl chain carnitines, propanoyl-carnitine and butanoyl-carnitine increased upon nitrogen-starvation. Moreover, the Calvin cycle may be de-regulated since sedoheptulose accumulated after nitrogen-depletion. Together the data provide now the basis for new strategies to improve lipid production and storage in Phaeodactylum strain Pt4.
authors.affiliation: Georg-August-University, Albrecht-von-Haller-Institute for Plant Sciences, Department of Plant Biochemistry, Justus-von-Liebig-Weg 11, 37077, Göttingen, Germany.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Popko
authors.affiliation: Georg-August-University, Albrecht-von-Haller-Institute for Plant Sciences, Department of Plant Biochemistry, Justus-von-Liebig-Weg 11, 37077, Göttingen, Germany.
authors.forename: Cornelia
authors.initials: C
authors.lastname: Herrfurth
authors.affiliation: Georg-August-University, Albrecht-von-Haller-Institute for Plant Sciences, Department of Plant Biochemistry, Justus-von-Liebig-Weg 11, 37077, Göttingen, Germany.
authors.forename: Kirstin
authors.initials: K
authors.lastname: Feussner
authors.affiliation: Georg-August-University, Albrecht-von-Haller-Institute for Plant Sciences, Department of Plant Biochemistry, Justus-von-Liebig-Weg 11, 37077, Göttingen, Germany.
authors.forename: Till
authors.initials: T
authors.lastname: Ischebeck
authors.affiliation: Georg-August-University, Albrecht-von-Haller-Institute for Plant Sciences, Department of Plant Biochemistry, Justus-von-Liebig-Weg 11, 37077, Göttingen, Germany.
authors.forename: Tim
authors.initials: T
authors.lastname: Iven
authors.affiliation: Rothamsted Research, Biological Chemistry, Harpenden, AL5 2JQ, United Kingdom.
authors.forename: Richard
authors.initials: R
authors.lastname: Haslam
authors.affiliation: Rothamsted Research, Biological Chemistry, Harpenden, AL5 2JQ, United Kingdom.
authors.forename: Mary
authors.initials: M
authors.lastname: Hamilton
authors.affiliation: Rothamsted Research, Biological Chemistry, Harpenden, AL5 2JQ, United Kingdom.
authors.forename: Olga
authors.initials: O
authors.lastname: Sayanova
authors.affiliation: Rothamsted Research, Biological Chemistry, Harpenden, AL5 2JQ, United Kingdom.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Napier
authors.affiliation: Microalgal Biotechnology Laboratory, The French Associates Institute for Agriculture and Biotechnology of Drylands, The Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus 8499000, Midreshet Ben-Gurion, Israel.
authors.forename: Inna
authors.initials: I
authors.lastname: Khozin-Goldberg
authors.affiliation: Georg-August-University, Albrecht-von-Haller-Institute for Plant Sciences, Department of Plant Biochemistry, Justus-von-Liebig-Weg 11, 37077, Göttingen, Germany.|Georg-August-University, Goettingen Center for Molecular Biosciences (GZMB), Department of Plant Biochemistry, Justus-von-Liebig-Weg 11, 37077, Göttingen, Germany.|Georg-August-University, International Center for Advanced Studies of Energy Conversion (ICASEC), Department of Plant Biochemistry, Justus-von-Liebig-Weg 11, 37077, Göttingen, Germany.
authors.forename: Ivo
authors.identifier: http://orcid.org/0000-0002-9888-7003
authors.initials: I
authors.lastname: Feussner
mesh_terms: D000214:Acyl Coenzyme A / Q000032:analysis; D001622:Betaine / Q000737:chemistry / Q000378:metabolism*; D018533:Biomass; D002952:Citric Acid Cycle; D017377:Diatoms / Q000254:growth & development / Q000378:metabolism*; D005227:Fatty Acids / Q000032:analysis / Q000378:metabolism*; D008401:Gas Chromatography-Mass Spectrometry; D006539:Heptoses / Q000378:metabolism*; D008027:Light; D055442:Metabolome / Q000528:radiation effects; D009584:Nitrogen / Q000378:metabolism*; D014280:Triglycerides / Q000378:metabolism*
chemical_list: D000214:Acyl Coenzyme A; D005227:Fatty Acids; D006539:Heptoses; D014280:Triglycerides; C003011:sedoheptulose; D001622:Betaine; D009584:Nitrogen