Sustainable agriculture and the use of plants for biomass and green chemistry will require biochemical plant engineering to re-channel plant metabolism. These objectives are impeded by our poor understanding of metabolic steps that control complex plant metabolic networks and the lack of an integrative, dynamic view of plant metabolism. It is therefore important to identify metabolic bottlenecks to guide plant breeding and to drive genetic engineering. A major aim of this project was to provide an integrated view of interactions between plant metabolic functions like photosynthesis, photorespiration, the Krebs cycle, N-assimilation, amino acid metabolism and NAD synthesis including post-translational regulatory mechanisms and metabolic fluxes. Complementary approaches including biochemistry, recombinant protein technologies, leaf gas exchange, 13C and 15N labelling, metabolomics, phosphoproteomics, and reverse genetics were used to achieve this. Major results include: The identification of light/dark differential phosphorylations of primary metabolism enzymes including photorespiratory proteins and enzymes involved in glycolytic and alternative serine biosynthesis pathways. Evidence showing NAD biosynthesis is a process that limits plant yield. A coordinated interplay between photosynthetic and photorespiratory activities is required for plant development in air since a blocked photorespiratory cycle negatively impacts photosynthesis thus altering C-allocation and RuBisCo amounts. The presence of an alternative pathway for respiratory C-delivery via lysine synthesis and recycling that contributes to metabolic flexibility. Prospects include carrying out translational biology to provide evidence that increasing NAD biosynthesis to improve yield is applicable to crop plants and the possibility to modulate protein phosphorylation to improve photosynthetic CO2 assimilation and yield.
An understanding of the basic processes of carbon and nitrogen assimilation and how they relate to plant biomass is of importance to guide plant breeding and to drive genetic engineering. The aim of this project was to provide an integrated view of interactions between photorespiration, photosynthesis, the TCA cycle, N-assimilation, NAD synthesis and amino acid metabolism including regulatory mechanisms and metabolic fluxes.
Major results include:
1. A light/dark differential phosphorylation of many major primary metabolism enzymes including photorespiratory proteins and 3-PGA-metabolizing enzymes.
2. NAD biosynthesis appears to limit plant yield.
3. The accumulation of photorespiratory metabolites inhibits photosynthetic CO2 assimilation and alters C-allocation.
4. Lysine synthesis and recycling can act as an alternative respiratory carbon source and contributes to metabolic flexibility.
1. Plant yield improvement by improving NAD synthesis.
2. The regulation of photorespiratory flux by protein phosphorylation.
3. The eventual estimation of in planta phosphoglycerate mutase activity by the quantification of its phosphorylation state.
Publications (as of July 2017):
Abadie C., Boex-Fontvieille E.R., Carroll A.J., Tcherkez G. (2016). In vivo stoichiometry of photorespiratory metabolism. Nature Plants 2: doi:10.1038/nplants.2015.1220.
Abadie C., Mainguet S., Davanture M., Hodges M., Zivy M., Tcherkez G. (2016). Concerted Changes in the Phosphoproteome and Metabolome Under Different CO2/O-2 Gaseous Conditions in Arabidopsis Rosettes. Plant and Cell Physiology 57(7): 1544-1556.
Boex-Fontvieille E., Daventure M., Jossier M., Zivy M., Hodges M., Tcherkez G. (2013). Photosynthetic Control of Arabidopsis Leaf Cytoplasmic Translation Initiation by Protein Phosphorylation. PLOS ONE 8(7): e70692.
Boex-Fontvieille E.R.A., Gauthier P.P.G., Gilard F., Hodges M., Tcherkez G.G.B. (2013). A new anaplerotic respiratory pathway involving lysine biosynthesis in isocitrate dehydrogenase-deficient Arabidopsis mutants. New Phytol 199(3): 673-682.
Boex-Fontvieille E., Davanture M., Jossier M., Zivy M., Hodges M., Tcherkez G. (2014). Photosynthetic activity influences cellulose biosynthesis and phosphorylation of proteins involved therein in Arabidopsis leaves. Journal of Experimental Botany 65(17): 4997-5010.
Boex-Fontvieille E., Daventure M., Jossier M., Hodges M., Zivy M., Tcherkez G. (2014). Phosphorylation pattern of Rubisco activase in Arabidopsis leaves. Plant Biology 16(3): 550-557.
Boex-Fontvieille E., Jossier M., Davanture M., Zivy M., Hodges M., Tcherkez G. (2014). Differential Protein Phosphorylation Regulates Chloroplast Movement in Response to Strong Light and Darkness in Arabidopsis thaliana. Plant Molecular Biology Reporter 32(5): 987-1001.
Dellero Y., Lamothe-Sibold M., Jossier M., Hodges M. (2015). Arabidopsis thaliana ggt1 photorespiratory mutants maintain leaf carbon/nitrogen balance by reducing RuBisCO content and plant growth. Plant Journal 83(6): 1005-1018.
Dellero Y., Mauve C., Boex-Fontvieille E., Flesch V., Jossier M., Tcherkez G., Hodges M. (2015). Experimental evidence for a hydride transfer mechanism in plant glycolate oxidase catalysis. Journal of Biological Chemistry 290(3): 1689-1698.
Dellero Y., Jossier M., Glab N., Oury C., Tcherkez G., Hodges M. (2016). Decreased glycolate oxidase activity leads to altered carbon allocation and leaf senescence after a transfer from high CO2 to ambient air in Arabidopsis thaliana. Journal of Experimental Botany 67(10): 3149-3163.
Dellero Y., Jossier M., Schmitz J., Maurino V.G., Hodges M. (2016). Photorespiratory glycolate-glyoxylate metabolism. Journal of Experimental Botany 67(10): 3041-3052.
Ghashghaie J., Tcherkez G. (2013). Chapter Eight - Isotope Ratio Mass Spectrometry Technique to Follow Plant Metabolism: Principles and Applications of 12C/13C Isotopes. In Advances in Botanical Research, R. Dominique, ed (Academic Press), pp. 377-405.
Hodges M., Jossier M., Boex-Fontvieille E., Tcherkez G. (2013). Protein phosphorylation and photorespiration. Plant Biology 15(4): 694-706.
Hodges M., Dellero Y., Keech O., Betti M., Raghavendra A.S., Sage R., Zhu X.G., Allen D.K., Weber A.P.M. (2016). Perspectives for a better understanding of the metabolic integration of photorespiration within a complex plant primary metabolism network. Journal of Experimental Botany 67(10): 3015-3026.
Tcherkez G. (2013). Is the recovery of (photo) respiratory CO2 and intermediates minimal? New Phytol 198(2): 334-338.
Communications in conferences:
Gordon conference “CO2 assimilation in plants”, Waterville, USA (June 2014): “Interactions between day respiration and photorespiration”, Guillaume Tcherkez.
Photorespiration: Key to better crops, Warnemünde, Germany (June 2015): “Protein phosphorylation and photorespiration”, Michael Hodges
Journées de la Sociéte Française de Photosynthèse, ENS Paris, France (June 2016): “The interaction between photosynthesis and photorespiration in Arabidopsis leaves”, Michael Hodges
Patent: De Bont L., Gakière B. French Patent 14 51445 « Plantes à rendement accru et méthode d’obtention de telles plantes » (2014), extension (24 fev 2015) PCT WO2015124799 : EP3110832A1 (Europe), US20160362702 (USA)