Glycerolipidome peculiarities of the smallest green picoeukaryote Ostreococcus tauri
2017
Degraeve-Guilbault, Charlotte | Bréhélin, Claire | Haslam, Richard | Sayanova, Olga | Marie-Luce, Glawdys | Jouhet, Juliette | Corellou, Florence | Laboratoire de biogenèse membranaire (LBM) ; Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS) | Rothamsted Research ; Biotechnology and Biological Sciences Research Council (BBSRC) | Physiologie cellulaire et végétale (LPCV) ; Institut National de la Recherche Agronomique (INRA)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG) ; Direction de Recherche Fondamentale (CEA) (DRF (CEA)) ; Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)) ; Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA) | Commissariat à l'énergie atomique et aux énergies alternatives (CEA) | Institut National de la Recherche Agronomique (INRA) | Université Grenoble Alpes [2016-2019] (UGA [2016-2019]) | Centre National de la Recherche Scientifique (grant PEPS ExoMOd); Region Aquitaine (project Omega-3) | ANR-11-INBS-0010,METABOHUB,Développement d'une infrastructure française distribuée pour la métabolomique dédiée à l'innovation(2011) | ANR-10-INBS-0004,France-BioImaging,Développment d'une infrastructure française distribuée coordonnée(2010)
The pico-alga Ostreococcus tauri is a minimal photosynthetic eukaryote that has been implemented as model system. O. tauri is known to efficiently produce docosahexaenoic acid (DHA). We provide a comprehensive study of the glycerolipidome of O.tauri and validate this species as model for related picoeukaryotes. Ostreococcus lipids displayed unique features that combined traits from the green and the chromoalveolate lineages. The betaine-lipid diacylglyceryl-hydroxymethyl-trimethyl-β-alanine and phosphatidyldimethylpropanethiol, both hallmarks of chromalveolates, were identified as presumed extraplastidial lipids. DHA was confined to these lipids while plastidial lipids of prokaryotic type were characterized by the overwhelming presence of ωω-3 C18-polyunsaturated fatty acids (PUFA), 18:5 being restricted to galactolipids. C16:4, a FA typical of green microalgae galactolipids, was also a major component of O. tauri extraplastidial lipids while 16:4-CoA species was not detected. Triacylglycerols (TAGs) displayed the complete panel of FAs and many species exhibited combinations of FAs diagnostic for plastidial and extraplastidial lipids. Importantly, under nutrient deprivation 16:4 and ωω-3 C18 PUFAs accumulated into de novo synthesized TAGs while DHA-TAGs species remained rather stable indicating an increased contribution of FAs of plastidial origin to TAG synthesis. Nutrient deprivation further severely downregulated the conversion of 18:3 to 18:4 resulting in obvious inversion of 18:3/18:4 ratio in plastidial lipids, triacylglycerols as well as in acyl-CoAs. The fine-tuned and dynamic regulation of 18:3/18:4 ratio suggested an important physiological role of these FAs in photosynthetic membranes. Acyl position in structural and storage lipids together with acyl-CoA analysis further help to apprehend mechanisms possibly involved in glycerolipid synthesis.
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