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Plant Physiol. 2016 Aug;171(4):2406-17. doi: 10.1104/pp.16.00718. Epub 2016 Jun 13.

Saturating Light Induces Sustained Accumulation of Oil in Plastidal Lipid Droplets in Chlamydomonas reinhardtii.

Author information

1
Commissariat à l'Energie Atomique, Centre National de la Recherche Scientifique Aix Marseille Université, Unité Mixte de Recherche 7265, Institut de Biosciences et Biotechnologies, Cadarache 13108, France (H.D.G., S.C., B.L., Y.L., P.A., H.J., F.B., G.P., Y.L.-B.);Faculty of Agriculture and the Environment, University of Sydney, Sydney, New South Wales 2006, Australia (H.D.G., B.J.); andCommissariat à l'Energie Atomique, INSERM, Université Grenoble Alpes, Institut de Biosciences et Biotechnologies de Grenoble, Grenoble 38000, France (S.B., M.T.).
2
Commissariat à l'Energie Atomique, Centre National de la Recherche Scientifique Aix Marseille Université, Unité Mixte de Recherche 7265, Institut de Biosciences et Biotechnologies, Cadarache 13108, France (H.D.G., S.C., B.L., Y.L., P.A., H.J., F.B., G.P., Y.L.-B.);Faculty of Agriculture and the Environment, University of Sydney, Sydney, New South Wales 2006, Australia (H.D.G., B.J.); andCommissariat à l'Energie Atomique, INSERM, Université Grenoble Alpes, Institut de Biosciences et Biotechnologies de Grenoble, Grenoble 38000, France (S.B., M.T.) yonghua.li@cea.fr.

Abstract

Enriching algal biomass in energy density is an important goal in algal biotechnology. Nitrogen (N) starvation is considered the most potent trigger of oil accumulation in microalgae and has been thoroughly investigated. However, N starvation causes the slow down and eventually the arrest of biomass growth. In this study, we show that exposing a Chlamydomonas reinhardtii culture to saturating light (SL) under a nonlimiting CO2 concentration in turbidostatic photobioreactors induces a sustained accumulation of lipid droplets (LDs) without compromising growth, which results in much higher oil productivity than N starvation. We also show that the polar membrane lipid fraction of SL-induced LDs is rich in plastidial lipids (approximately 70%), in contrast to N starvation-induced LDs, which contain approximately 60% lipids of endoplasmic reticulum origin. Proteomic analysis of LDs isolated from SL-exposed cells identified more than 200 proteins, including known proteins of lipid metabolism, as well as 74 proteins uniquely present in SL-induced LDs. LDs induced by SL and N depletion thus differ in protein and lipid contents. Taken together, lipidomic and proteomic data thus show that a large part of the sustained oil accumulation occurring under SL is likely due to the formation of plastidial LDs. We discuss our data in relation to the different metabolic routes used by microalgae to accumulate oil reserves depending on cultivation conditions. Finally, we propose a model in which oil accumulation is governed by an imbalance between photosynthesis and growth, which can be achieved by impairing growth or by boosting photosynthetic carbon fixation, with the latter resulting in higher oil productivity.

PMID:
27297678
PMCID:
PMC4972293
DOI:
10.1104/pp.16.00718
[Indexed for MEDLINE]
Free PMC Article

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