LEMNAMASS - Bases moléculaires de l efficacité de la photosynthèse chez Lemnoideae, un nouveau modèle de biomasse

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1 Journées de restitution 2017 PEPS Exo Mod LEMNAMASS - Bases moléculaires de l efficacité de la photosynthèse chez Lemnoideae, un nouveau modèle de biomasse Pr Gilles Comte, Responsable du Centre d'etude des Substances Naturelles, UMR 5557 CNRS-Université de Lyon, Ecologie Microbienne, Faculté de Sciences - Université de Lyon. Pr Thomas Pfannschmidt: Laboratoire de Physiologie Cellulaire et Végétale (LPCV) Team 7: Nucleo-plastidic Interaction Chloroplast biogenesis and redox control Univ. Grenoble-Alpes / CNRS (UMR5168) / INRA (USC1359) / CEA GRENOBLE

2 The problem Historic development of world population Zhu, Long, Ort 2010 Annu Rev Plant

3 One possible solution : Improvement of photosynthesis Zhu, Long, Ort 2010 Annu Rev Plant

4 One possible solution : Improvement of photosynthesis Zhu, Long, Ort 2010 Annu Rev Plant

5 Science Nov 18;354(6314): Improving photosynthesis and crop productivity by accelerating recovery from photoprotection. Kromdijk J 1, Głowacka K 2,3, Leonelli L 4, Gabilly ST 4, Iwai M 4,5, Niyogi KK 6,5, Long SP 2,7. Author information Abstract Crop leaves in full sunlight dissipate damaging excess absorbed light energy as heat. When sunlit leaves are shaded by clouds or other leaves, this protective dissipation continues for many minutes and reduces photosynthesis. Calculations have shown that this could cost field crops up to 20% of their potential yield. Here, we describe the bioengineering of an accelerated response to natural shading events in Nicotiana (tobacco), resulting in increased leaf carbon dioxide uptake and plant dry matter productivity by about 15% in fluctuating light. Because the photoprotective mechanism that has been altered is common to all flowering plants and crops, the findings provide proof of concept for a route to obtaining a sustainable increase in productivity for food crops and a much-needed yield jump.

6 The photosynthetic apparatus

7 Structure and Function of Chloroplasts Highly complex thylakoid membrane system Photosynthesis Reduction of sulfur and nitrogen Biosynthesis of -vitamins -aminoacids -lipids -secondary metabolites proteins (50 plastid-encoded)

8 Allen and Forsberg (2001), Trends Plant Sci. Photosystem II structure

9 PSII can be remodelled Dekker and Boekema 2005 BBA Dietzel et al Plant Cell

10 Redox control of photosystem II structure Iwai et al Plant Cell

11 Redox control of photosystem II structure Dietzel et al Plant Cell

12 Light intensity Light intensity Plant populations contain strong light gradients PAR Spectrum FR m; ~ 1000 µe High light stress 2.2 m; ~ 200 µe Wavelength / nm 1.5 m; ~ 50 µe Spectrum Low light stress m; ~ 20 µe Wavelength / nm

13 Light gradients in dense plant populations Wagner et al. 2006, BioForum

14 Ort et al. 2015

15 Re-building nature in the lab

16 A light system that mimicks light quality gradients PSII-Light PSI-Light

17 Excitation imbalances between the photosystems induce redox signals PSII-light PSI-light PSII e - Cyt PSI PSII Cyt e - PSI PQH 2 bf PQ bf

18 Chlorophyll fluorescence as indicator for acclimation PSI PSII Bonardi et al. (2005) Nature 437 Fs/Fm Top Middle Bottom 0 0,02 0,04 0,06 0,08 0,1 0,12 Wagner et al. (2008) Planta 228 Steiner et al. (2009) Mol. Plant. 2

19 Light gradients: Adaptation vs. non-adaptation. Strong 3D structure High leaf area index (LAI) Simple 2D structure Low leaf area index (LAI) PSII must be adaptable to all positions in the plant stand: optimisation to light harvesting and photoprotection is spatially separated LAI: 8-15 LAI: 1 PSII can be optimized to light harvesting and photoprotection at the same time

20 A candidate for 2D photosynthesis - duckweeds Natural conditions Phylogenetic tree Wolffia arrhiza Spirodela polyrhiza Lemna minor

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23 Advantages of duckweeds Biology - The smallest flowering plants - Multiply by vegetative budding - Occur ubiquitiously in all sweet waters on Earth Biotechnology - Exponential growth (biomass doubling in 48 hours) - Phytoremediation of municipal wastewater - Removal of algae blooms in eutrophic lakes - Biomass can be used for feeding cattle or bioethanol - EU ISO norm for heavy metal intoxication of water Experimental biology - Spirodela genome sequenced Easy cultivation - Forgotten model of photosynthesis research

24 Tripling biomass in six days

25 Easy to culture and harvest

26 Light acclimation in duckweeds WL PSI PSI-II PSII PSII-I Lemna minor chlorophyll fluorescence parameters, starch and Chl accumulation. Lemna minor two-dimensional Chl fluorescence.

27 Differences in thylakoid membrane proteins. A kda B kda * * * * * Coomassie PSI-A ATPase C CP43 P-core P-LHCII Cytf kda D1 Phospho-Immuno-blot 25 LHCII

28 PSII supercomplex remodelling in Lemna differs from that in Arabidopsis. Lemna Arabidopsis PSII megacomplex PSII supercomplexes PSI, PSII dimer, ATP synthase PSII monomers Cyt b6f LHCII trimers LHCII monomers * * * *

29 2D BN PAGE Arabidopsis kda PsaA/B AtpA/B CP47 P-CP43 CP43 D2 D1 LHCII * * 25 PSI/Cyt SUs PSII PSII PSI

30 2D BN PAGE Lemna kda PsaA/B AtpA/B CP47 CP43 D2 D1 LHCII PSI/Cyt SUs PSII PSII-I 3 d

31 AtpA/B CP47 CP43 D2 D1 LHCII PSI/ Cyt SUs Lemna Arabidopsis

32 Differences in Lemna photosynthesis apparatus 1. Lack of state transitions 2. No redox dependent PSII remodelling 4. CP43 / Cytf size variation (post-translational modifications?) 3. Specific changes in LHCII and CP43 phosphorylation 5. Novel subunit in PSII super-complexes? 6. Missing small subunits of PSI 7. Additional PSII super-complex

33 Ecological adaptation of Lemna photosynthesis 1. 2D photosynthesis does not require light quality acclimation (Lack of competition for light?) 2. 2D photosynthesis has adapted specific proteins in size and phosphorylation state (reason for 1.?) 3. 2D photosynthesis may have generated novel PSII structures (optimization of light harvesting?) 4. 2D photosynthesis may have eliminated PSI subunits (acceleration of electron flow?)

34 INRA Equipe 7 Nucleo-plastidic interaction Chloroplast biogenesis and redox control LEMNAMASS: Robert Blanvillain Fabien Chevalier Florence Courtois Björn Grübler Elisabeth Hommel Silva Lerbs-Mache Monique Liebers Livia Merendino Thomas Pfannschmidt Funding: Collaborators: Gilles Comte Laurent Legendre Marjolaine Rey AGIR2015 PEPS ExoMod 2016 Research Unit 804