Christophe Six

1. Unité d’Enseignement : Evolution du Phytoplancton Marin et Biogéochimie Introduction to Photosynthesis: Evolutionaryprocesses Christophe Six UMR UPMC-CNRS 7144 “Adaptation & Diversité en Milieu Marin" Equipe « Procaryotes Photosynthétiques Marins » Station Biologique de Roscoff Université Pierre et Marie Curie (Paris VI) Bureau 354, 3ème étage (Bâtiment GT) six@sb-roscoff.fr

2. h Organic matter Minerals Cofactors . Most of life on Earth is dependent on photosynthesis through food webs. Exception : hydrothermal vents What is photosynthesis ? Sensu lato: Anysynthesis of organicmatterthatis light dependent Common Sense: All processes used by phototrophic organisms using chlorophyll compounds to convert light energy into chemical energy (ATP).

3. Precambrian Millions years http://www.ipgp.jussieu.fr/files_lib/83_echm-gt.gif Origin of photosynthesis at thescale of Geological times Millions years Millions years

4. Microfossils of filamentous cyanobacteria West of Australia http://www.interet-general.info/IMG/Stromatolites-2-3.jpg http://www.gc.maricopa.edu/earthsci/imagearchive/stromatolite.jpg http://www.cartage.org.lb/en/themes/Sciences/Paleontology/Paleozoology/Precambrian/Precambrian.htm The oldest fossils : the Stromatolites Stromatolites

5. Fossil evidences : the stratified iron formations Iron stratified formations Microbial coccoid fossil (Eosphaera) Mont Bruce, West of Australia http://www.geo.vu.nl/~smit/hamersley/hamersley%20iron.jpg 10 µm Formation of Gunflint, North America http://gsc.nrcan.gc.ca/paleochron/05_e.php http://z.about.com/d/geology/1/0/d/-/1/bifslab.jpg http://www.cartage.org.lb/en/themes/Sciences/Paleontology/Paleozoology/Precambrian/mich03.gif

6. Consequences of the development of oxygenicphotosynthesis Diversité (nombre de taxa) Présent Billion years

7. The photosyntheticorganisms on Earth . Sulphurous green bacteria Chlorobium, Prosthecochloris, Pelodictyon, Ancalochloris, Chloroherpeton . Non-sulphurous green bacteria Chloroflexus, Chloronema, Heliothrix, Roseiflexus . Non-Sulphurous purple bacteria Rhodospirillum, Rhodobacter, Rhodopseudomonas, Rhodomicrobium . Sulphurous purple bacteria Chromatium, Thiospirillum, Thiopedia . Les heliobacteria Heliobacterium . Photoheterotrophic, anoxygenic, aerobic bacteria Roseobacter, Roseovarius, Erythrobacter . Cyanobacteria = Oxyphotobacteria Synechococcus, Prochlorococcus, Oscillatoria, Anabaena, Synechocystis, Microcystis, Planktothrix, Trichodesmium, Croccosphaera, etc… . Photosynthetic (oxygenic) eukaryotes Rhodophyta, Heterokontophyta, Chlorobionta Lakes & Estuaries Benthic/Planctonic. Stratified freshwater lakes: Anoxiques zones Stillpoorlyknown; Oceans

8. Oxygenic Two types of reaction centres Antenna = Phycobilisome or Lhc Electron donnors = H2O Anoxygenic A single type of reaction centre -Typical antenna system (BChl & Carotenoids) Electron donnors = reduced compounds Aérobic RC I + RC II Cyanobacteria = oxyphotobacteria (photohétérotrophs & obligatory phototrophs) Photosynthetic eukaryotes: Eukaryotic phytoplankton, macroalgae, bryophytes and vascular plants Aerobic Anaerobic (photohétérotrophs) Green bacteria (Chlorosome – no RuBisCO) Héliobacteria Purple bacteria (RC II – BChl a ou b – (Calvin cycle) RC I Sulphurous (obligatory phototrophs) Non- sulphurous (photoheterotrophs) Sulphurous (obligatory phototrophs) RC I Non- sulphurous (photoheterotrophs) RC II Chloroflexaceae Chlorobiaceae The different groups of photosyntheticorganisms on Earth Photosynthesis

9. Anoxygenic photosyntheses

10. Bactériochlorophylle b Bactériochlorophylle a Reaction centres and bacteriochlorophylls

11. Sulphurous Green bacteria Chlorobium tepidum Chlorobium sp. BS1 Microbial mat : Chlorobium Yellowstone national park, USA Microbewiki Benthic organisms : 1mm beneath the sediment at the bottom of lakes and estuaries

13. The antenna complex of Chlorobium spp.

14. The reaction centre of Chlorobium spp. . 3 proteins : 2 proteins A (65 kDa) + 1 small proteine C de 8 kDa  Cofactors linked to these proteins constituting a double, transmembrane, redox chain . Chargeseparation: expulsion of an e- from a Bchl a P840, . Transfer to an acceptor A0 which has a low redox potential, then to A1 = naphtoquinone

15. The reaction centre of Chlorobium spp. . Electron tranfer to three Iron-Sulphur clusters, named FX, FA et FB . 2 ferredoxins 2 e- + NAD+ + H+ NADH (universalreductant of metabolicreactions) => 2 excitons are necessary to produce one molecule of NADH Fd soluble

16. Le centre réactionnel de Chlorobium spp. . Cytochromic system c553 : complexed (4 hemes) or soluble  e- given back to P840 . c553reduced by flavocytochrome c551 (1 heme + 1 flavin group) . 2 C551 + S2-  C551 + 2 e- + S  Sulphur is released in the periplasm

17. Cyclic transport of e- The electron carrier chain of Chlorobiumspp.

18. Non-sulphurous purple bacteria Rhodospirillum rubrum Rhodobacter sphaeroides http://www.de.mpi-magdeburg.mpg.de/research/projects/1010/1014/1020/rhodos.jpg http://www.martin-stein.com/images/rhodob.jpg Rhodopseudomonas sp.

19. Different types of structures of inner foldings of the plasmic membrane Non-sulphurous purple bacteria Rhodobacter sp.

20. The innerfoldings of Rhodobactersphaeroides (chromatophores)

21. The antenna complex of Rhodopseudomonas acidophila - LH2 complex : hollow cylinder constituted by 9 motifs = 9 paires de polypeptide  et  (5-7 kDa) - The 9  are in periphery, the 9 are inner ; bacteriochlorophylls are located between these two crowns - On pair  binds 1 ou 2 BChl  18 BChl perpendicular to the plan per LH2 (= B850 abs max at 850nm) - The  subunits bind an additional molecule of BChl between two -helices, parallel to the plan These 9 BChl = B800 (abs max à 800nm) - One carotenoid is linked to each  Bleu : Polypeptides Orange : B800 bacteriochlorophylls Vert : Carotenoids

22. The reaction centre of non-sulphurous purple bacteria Rhodobacter sphaeroides Rhodopseudomonas viridis

23. Photosyntheticapparatus of Rhodobactersp. Protein Structure involved in the photosynthetic activity of Rhodobacter sp. (Cross section of the cytoplasmic membrane)

24. Cyclic electron transport in Rhodobacter sp.

25. Anoxygenic reaction centres

26. Oxygenic photosynthesis

27. Synechococcus sp. Marine chloroplasts Fucus sp. Bryopsis sp. Porphyridium sp. Oxygenic photosynthesis n [CO2 + H2O] [CH2O] n + O2 Global reaction : Location : Chloroplasts of vascular plants

28. Stroma/cytosol Lumen Stroma/cytosol Membranar lipids Photosynthetic membranes : the thylacoids

29. The membranar photosynthetic complexes

30. Whatis a photosystem? Photosystem = reaction centre + photosynthetic antenna . External antenna : the major one . Two large subunits D1/D2 ; PsaAB) . Inner antenna stuck to the reaction centre : the minor one . A number of small subunits . The charge separation : one electron is extracted from a chlorophyll molecule and released in a chain of acceptors Chl (=P680) chl* (=P680*) + e-

31. Photosystem II antennae . Large diversity of configuration  depending on the taxonomic group . Two major structural groups : intrinsic et extrinsic to the thylacoids

32. LHC type proteins Intrinsic antennae Intrinsic, major PSII antenna (LHC type) PS Thylacoids

33. Intrinsic antennae Proteins LHC Reaction centres (Top view)

34. Pigments associated to intrinsicantennae . Chemotaxonomy Chla 19'-hexanoyloxyfucoxanthin Chl b Chl c1 Chl c2 Lutein Peridinin Chl c3 Neoxanthin Fucoxanthin Prasinoxanthin . Differentroles of the xanthophylls: light harvesting & photoprotection Violaxanthin Diadinoxanthin Antheraxanthin Diatoxanthin Zeaxanthin

35. Pigments associated to intrinsicantennae Chlorophylls a et b

36. Chl c Absorption properties of chlorophylls

37. -carotene (vitamin A) -carotene Carotenoids

38. Carotenoids: xanthophylls

39. Carotenoids: absorption properties -Carotene Fucoxanthin Diadinoxanthin Lutein Zeaxanthin

40. Organisms with extrinsic, photosynthetic antennae Rhodophyta Cyanophyta Cryptophyta

41. Phycobiliproteins

42. Phycobiliproteins Allophycocyanin (AP) Phycocyanin (PC) Phycoérythrocyanin (PEC) Phycoérythrin (PE) . 4 classes of phycobiliproteins : . The classes of phycobiliproteins are differentiatated by: • The aminoacid sequence of the  and  chains (between 15 and 20 kDa) • The composition in phycobilins, and therefore their spectral properties Phycocyanobilin (PCB) Phycobiliviolin (PVB) Phycoérythrobilin (PEB) Phycourobilin (PUB) . 4 classes of phycobilins :

43. Phycobilins PUB Phycourobilin PXB PEB PCB Phycoerythrobilin Phycyanobilin

44. Phycobilin Biosynthesis

45. Phycoerythrins Phycobiliproteins and phycobilins Chromophores donnor vs. Chromophore acceptor The phycobilin placed at -84 Is always the acceptor chromophore, whatever the phycobiliprotein

46. 75 75 83 83 250/61 140 140 159 159 282 159 159 140 140 282 282 83 250/61 75 250/61 83 75 83 83 75 75 140 -140 -159 159 Hexameric PEII diagram  PEII dimer Modified after Wilbanks et al. (1991) Phycobiliproteins and phycobilins Synechococcus sp. WH8103

47. Optical properties of phycobiliproteins PCB PEB PEB PUB Absorbance Wavelength (nm) C-Phycocyanin

48. Phycobilisomes of Calothrix sp. PCC 7601 (Sidler, 1994) Hexamer ()6 The phycobilisome . Phycobiliprotein hexamers aggregate in macrostructures: Allophycocyanin Phycoerythrin Phycocyanin 11 nm 6 nm coeur Bras

49. SDS-PAGE (15% acr.) of phycobilisomes fractions Synechococcus sp. PCC7002 (1), Anabaena sp. PCC7120 (2), Mastigocladus laminosus (3) ; Weigh markers (4). (M. laminosus, Reuter and Nickel-Reuter, 1993) Subunits  &  Linkers Phycobilisome linker polypeptides

50. Oriented transport of energy in the phycobilisome