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Increasing Absorption Range for Photosynthesis

Increasing Absorption Range for Photosynthesis. http://media-2.web.britannica.com/eb-media/30/27030-004-293E0372.jpg. Goals. Express different photosynthetic pigments in cyanobacteria Increase the wavelengths that can absorb light energy and transfer to photosynthetic machinery

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Increasing Absorption Range for Photosynthesis

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  1. Increasing Absorption Range for Photosynthesis http://media-2.web.britannica.com/eb-media/30/27030-004-293E0372.jpg

  2. Goals • Express different photosynthetic pigments in cyanobacteria • Increase the wavelengths that can absorb light energy and transfer to photosynthetic machinery • Potentially increase efficiency? http://www.emc.maricopa.edu/faculty/farabee/BIOBK/pigment.gif

  3. Photosynthetic Pigments Chlorophylls Phycobilins Β carotene Carotenoids http://www.food-info.net/uk/colour/chlorophyll.htm http://www.mbari.org/staff/conn/botany/reds/daisy/phycocyanobilin.gifhttp://upload.wikimedia.org/wikipedia/commons/d/da/Beta-carotene.png

  4. How do the Photo-Pigs work? • Chlorophylls • Transfers electrons around → reaction center • Incorporated into photosystem protein complexes • Carotenoids • Membrane bound • Transfers electrons to chlorophyll • Phycobilins • Water soluble, in cytoplasm • Also transfers electrons to chlorophyll

  5. Model Organism: Cyanobacteria • Synechococcus, Synechocystis sp. PCC6803 • Chlorophyll a, Phycobilins (phycocyanin, allophycocyanin, allophycocyanin B, phytoerythrin) • Genetically tractable

  6. What has been done before? • Expressed chlorophyll b in Synechocystis sp. PCC6803 • Demonstrated that it is incorporated into P700 chlorophyll-protein complex Satoh et al., Journal of Biological Chemistry, 2001 276 (6)

  7. What can we do?

  8. Idea 1: BioBrick: Bba_K152005 • Four enzymes required for beta-carotene synthesis: • geranylgeranyl diphosphate synthase (CrtE - BbaK152001) • phytoene synthase (CrtB - BbaK152002) • phytoene dehydrogenase (CrtI - BbaK18003) • lycopene beta-cyclase (CrtY - BbaK152003)

  9. Carotenoid Biosynthesis in Synechococcus

  10. Questions to ask / Things to do • When overexpressed is beta-carotene incorporated into a photosystem? • What does beta-carotene normally do in cyanobacteria? • How/Why was this biobrick made? What did they feed the E. coli? • Can E. coli constructs be used in cyanobacteria?

  11. Idea 2: Express Chlorophyll d • Spectrum is red shifted • Can act as reaction center? • Need to find protein that cando this reaction. Larkum and Kuhl, Trends in Plant Science (2005) 10 (8).

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