Transcript 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.

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
• Potentially increase
efficiency?
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/pigment.gif
Photosynthetic Pigments
Chlorophylls
Phycobilins
Β carotene
http://www.food-info.net/uk/colour/chlorophyll.htm
http://www.mbari.org/staff/conn/botany/reds/daisy/phycocyanobilin.gif
http://upload.wikimedia.org/wikipedia/commons/d/da/Beta-carotene.png
Carotenoids
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
Model Organism: Cyanobacteria
• Synechococcus, Synechocystis sp. PCC6803
• Chlorophyll a, Phycobilins (phycocyanin,
allophycocyanin, allophycocyanin B,
phytoerythrin)
• Genetically tractable
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)
What can we do?
Idea 1: BioBrick: Bba_K152005
• Four enzymes required for beta-carotene
synthesis:
1. geranylgeranyl diphosphate synthase (CrtE BbaK152001)
2. phytoene synthase (CrtB - BbaK152002)
3. phytoene dehydrogenase (CrtI - BbaK18003)
4. lycopene beta-cyclase (CrtY - BbaK152003)
Carotenoid Biosynthesis in Synechococcus
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?
Idea 2: Express Chlorophyll d
• Spectrum is red shifted
• Can act as reaction center?
• Need to find protein that can
do this reaction.
Larkum and Kuhl, Trends in Plant Science (2005) 10 (8).