Single cell c4 photosynthesis


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Single cell c4 photosynthesis

  1. 1. Single cell C4 photosynthesisA.T. WickramageBS/2008/220
  2. 2. Contents01 • Photosynthesis02 • Calvin cycle03 • Four Carbon (C4) pathway04 • Kranz anatomy05 • Single cell C4 photosynthesis06 • Terrestrial single cell C4 photosynthesis07 • Cell compartmentalization08 • Aquatic single cell C4 photosynthesis09 • Discussion10 • References2
  3. 3. • The transduction of the energy of sunlight tochemical energy by green plants is called asphotosynthesis.6CO2 + 6H2O C6H12O6 + 6O2Two types of reactions in photosynthesis• Light dependent reactions• Light independent reactions3Photosynthesis
  4. 4. 4Schematic diagram of the overall organization of the membranes in the chloroplast
  5. 5. The light dependent reactions• Occur in the thylakoid membrane• Converts light energy to chemical energy• Chlorophyll and several other accessory pigments areinvolved• Final products– NADPH– ATP– O25
  6. 6. Light independent reactions – The fixationof CO2• Take place in the stroma within the chloroplast• Converts CO2 to sugar• Involves the Calvin cycle• Two basic types of photosynthetic mechanisms– C3– C46
  7. 7. Calvin cycle• Chemical energy harvested by the light dependentreactions, used to reduce carbon (CO2)• The Calvin cycle consists of three main parts– Carboxylation– Reduction– Regeneration7
  8. 8. 8A summary of the Calvin cycle3 ATP6 NADPH6 ATP
  9. 9. Four Carbon (C4) pathway• In some plants, the first product of CO2 fixation is not thethree-carbon molecule 3-PGA, but four-carbon moleculeoxaloacetate (OAA).• The C4 photosynthetic carbon cycle is an elaborated additionto the C3 photosynthetic pathway.• It evolved as an adaptation to– high light intensities– high temperatures– suppress photorespiration– increase carbon gain (Edwards et al., 2010)• Associates with the Kranz anatomy9
  10. 10. Kranz anatomy• Thereby,– Oxygenase reaction and the following photorespiration are repressed– Rubisco accumulates in BSCs chloroplasts– phosphoenolpyruvate carboxylase (PEPC) accumulate in the cytoplasm andchloroplasts of MCs– MCs and BSCs show differences in the biochemistry of carbon fixation.– Division of labor achieved (Hatch, 1987)10Diagram of C4 leaf cross section• Wrapping of vascular bundles by two specialized cell types, the mesophyll cells (MCs)and bundle sheath cells (BSCs)• To concentrate CO2 around Rubisco
  11. 11. 11Leaf cross section of Panicum miliaceum, which exhibits Kranz anatomyMesophyll cellBundle sheath cell(Source:
  12. 12. 12An electron micrograph of grana- deficient chloroplasts in bundle sheathcells and granal chloroplasts in mesophyll cells.(Source: cell chloroplast(Granal chloroplast)Bundle sheath cell chloroplast(Grana deficient Chloroplast)Starch granuleGrana
  13. 13. The C4 pathway consists of three key steps1. Initial fixation of CO2 by phosphoenolpyruvate carboxylase(PEPC) to form a C4 acid2. Decarboxylation of a C4 acid to release CO2 near the site ofthe Calvin cycle3. Regeneration of the primary CO2 acceptorphosphoenolpyruvate (PEP)13
  14. 14. 14A diagram showing a summary of metabolic division of labor in mesophyll cellsand bundle sheath cells of C4 plantsMesophyll cell Bundle sheath cell1 23
  15. 15. Single cell C4 photosynthesis• Kranz type leaf anatomy was synonymous with C4photosynthesis.• Single cell C4 photosynthesis lacks Kranz anatomy.• Two types1. Terrestrial single cell C4 photosynthesis2. Aquatic single cell C4 photosynthesis15
  16. 16. Terrestrial single cell C4 photosynthesis1. Bienertia cycloptera2. Bienertia sinuspersici3. Suaeda aralocaspica16
  17. 17. The family Chenopodiaceae• A family of flowering plants, also called the Goosefoot Family.• Contains approximately 1300 species worldwide and rangefrom annual herbs to trees.• Majority are weeds and many are salt and drought tolerant.• Many chenopod species have C4 photosynthesis.17
  18. 18. Bienertia cycloptera• Widespread in Central Asia• Grows in salty depressions• Plant is usually shorter, precise measurements are notavailable.• Flowering time is from July to August and fruiting periodis in SeptemberA photograph of Bienertia cycloptera18
  19. 19. Bienertia sinuspersici• Distribution is restricted to Persian Gulf areas and Baluchistan• Plant height is up to 130-160 cm• Flowering time is October and fruiting period is fromNovember to DecemberA photograph of Bienertia sinuspersici19
  20. 20. Suaeda aralocaspica• Restricted to the deserts of central Asia• It is a monoecious, annual, halophyte.• Grows to a height of between 20- 50 cmA photograph of Suaeda aralocaspica20
  21. 21. • Lacks Kranz anatomy• Compartmentalization of organelles and photosyntheticenzymes into two distinct regions within a single cell• Cytoskeleton associates with the positioning of chloroplastsand other organelles• Lack of night time CO2 fixation• Function with a unique C4 mechanism21Features of single cell C4 photosynthesis
  22. 22. Cell compartmentalization (1)• In Suaeda aralocaspica– Two chloroplast types are arranged in cylindrical chlorenchyma cells.– Spatially separated to opposite ends of the cell22ProximalcompartmentDistalcompartmentMicroscopy image of the distal and proximalcompartments in S. aralocaspicaNucleus
  23. 23. • Distal compartment– Lack grana– Pyruvate, Pi dikinase (PPDK) is present– No starch– C4 carbon fixation• Proximal compartment– Rubisco is concentrated– NAD-malic enzyme is present– C3 carbon fixation23Microscopy image of immunolocalization ofphotosynthetic enzymes S.aralocaspicaRubiscoPPDK
  24. 24. • In Bienertia Species– One chloroplast type in the periphery [peripheral chloroplast (P-CP)]– Other chloroplast type (central compartment chloroplast [C-CP]) in central– Compartments are spatially separated by a vacuole– Cytoplasmic compartments are interconnected by cytoplasmic channels(Voznesenskaya et al., 2002; Edwards et al., 2004)24Peripheral compartmentCentral compartmentNucleusMicroscopy image of the peripheral andcentral compartments in B. sinuspersiciCell compartmentalization (2)
  25. 25. • Peripheral cytoplasmic compartment (PCC)– Less number of mitochondria– Has grana-deficient chloroplasts– Contain pyruvate, Phosphate dikinase,Phosphoenolpyruvate carboxylase– C4 carbon fixation• Central cytoplasmic compartment (CCC)– Filled with mitochondria and granal chloroplasts– Rubisco is abundant– C3 carbon fixation25
  26. 26. 26The actin cytoskeleton in chlorenchyma cells of B. sinuspersici (left) andS. aralocaspica (right)Actin cytoskeleton( Source: Chuong et al., 2006)
  27. 27. CO2 concentration mechanism in Bienertia species27
  28. 28. Aquatic single cell C4 photosynthesis• CO2 HCO3- in water• The availability of inorganic carbon for photosynthesis in wateris limited by diffusion and pH.• Some eukaryotic phytoplankton/ angiosperm species haveevolved energy dependent mechanisms for concentrating CO2.1. Thalassiosira weissflogii2. Hydrilla verticillata28
  29. 29. Thalassiosira weissflogii• Centric, unicellular diatom• Found in marine environments and also in inland waters inmany parts of the world• Initial incorporation of CO2 into four carbon acids and thesubsequent transfer of carbon to 3-phosphoglycerate andsugarsImage of Thalassiosira weissflogii29
  30. 30. Hydrilla verticillata• Found in fresh water environments• C4 photosynthesis is accomplished without anycompartmentation and chloroplast differentiation.• A facultative C4 plant30A photograph of Hydrilla verticillata
  31. 31. Discussion• Many important crops are C3 plants.• The solar energy conversion efficiency to biomass is lower in C3photosynthesis than that of C4 photosynthesis.• C4 plants were evolved from C3 plants, acquiring the C4 photosyntheticpathway in addition to the C3 pathway.• Transfer of C4 traits to C3 plants has been one strategy for improving thephotosynthetic performance of C3 plants.• This was initially attempted by means of conventional hybridization betweenC3 and C4 plants and more recently using transgenic techniques.– e.g. C4 rice project31
  32. 32. • Akhani, H., Barroca, J., Koteeva, N., Voznesenskaya, E., Franceschi, V., Edwards, G., Ghaffari, M., and Ziegler, H.(2005). Bienertia sinuspersici (Chenopodiaceae): a new species from Southwest Asia and discovery of a thirdterrestrial C4 plant without Kranz anatomy. Systematic Botany 30(2): 290–301.• Bowes, G., Rao, S.K., Estavillo, G.M., Reiskind, J.B. (2002). C4 mechanisms in aquatic angiosperms:comparisons with terrestrial C4 systems. Functional Plant Biology 29: 379–392.• Brown, R.H., Bouton, J.H. (1993). Physiology and genetics of inter specific hybrids between photosynthetictypes. Annual Review of Plant Physiology and Plant Molecular Biology 44: 435–456.• Chuong, S.D.X., Franceschi, V.R., and Edwards, G.E. (2006). The cytoskeleton maintains organelle partitioningrequired for single-cell C4 photosynthesis in Chenopodiaceae Species. The Plant Cell 18: 2207–2223.• Edwards, G.E., Franceschi, V.R., Voznesenskaya, E.V. (2004). Single cell C4 photosynthesis versus the dual-cell(Kranz) paradigm. Annual Review of Plant Biology 55, 173–196.• Fukayama, H., Tsuchida, H., Agarie, S. (2001). Significant accumulation of C4-specificpyruvate, orthophosphate dikinase in a C3 plant, rice. Plant Physiology 127, 1136–1146.• Hatch, M.D. (1987). C4 photosynthesis: a unique blend of modified biochemistry, anatomy and ultrastructure.Biochimica et Biophysica Acta 895, 81–106.• Hausler, R.E., Hirsch, H.J., Peterhansel, K.F. (2002). Overexpression of C4-cycle enzymes in transgenic C3 plants:a biotechnological approach to improve C3-photosynthesis. Journal of Experimental Botany 53, 591–607.32References
  33. 33. • Lara, M.V., Chuong, S.D.X., Akhani, H., Andreo, C.S., and Edwards, G.E. (2006). Species having C4 single-cell-type photosynthesis in the Chenopodiaceae family evolved a photosynthetic Phosphoenolpyruvatecarboxylase like that of Kranz-type C4 species. Plant Physiology 142: 673–684.• Miyao, M., Masumoto, C., Miyazawa, S., and Fukayama, H. (2011). Lessons from engineering a single-cellC4 photosynthetic pathway into rice. Journal of Experimental Botany 62(9): 3021–3029.• Offermann, S., Okita, T.W., and Edwards, G.E. (2011). Resolving the Compartmentation and Function of C4Photosynthesis in the Single-Cell C4 Species Bienertia sinuspersici. Plant Physiology 155: 1612–1628.• Voznesenskaya, E.V., Edwards, G.E., Kiirats, O., Artyusheva, E.G., and Franceschi, V.R. (2003). Developmentof biochemical specialization and organelle partitioning in the single celled C4 system in leaves ofBorszczowia aralocaspica (Chenopodiaceae). American Journal of Botany 90, 1669–1680.• Voznesenskaya, E.V., Franceschi, V.R., and Edwards, G.E. (2004). Light-dependent development of singlecell C4 photosynthesis in cotyledons of Borszczowia aralocaspica (chenopodiaceae) during transformationfrom a storage to a photosynthetic organ. Annals of Botany 93: 177-187.• Voznesenskaya, E.V., Franceschi, V.R., Kiirats, O., Artyusheva, E.G., Freitag, H., and Edwards, G.E. (2002).Proof of C4 photosynthesis without Kranz anatomy in Bienertia cycloptera (Chenopodiaceae). The PlantJournal 31: 649–662.• Voznesenskaya, E.V., Franceschi, V.R., Kiirats, O., Freitag, H., and Edwards, G.E. (2001). Kranz anatomy is notessential for terrestrial C4 plant photosynthesis. Nature 414: 543–54633
  34. 34. Thank you34