Measurement of a possible signal for nitrogen starvation in a cyanobacterium-plant symbiosis

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Measurement of a possible signal for nitrogen
starvation in a cyanobacterium-plant symbiosis
Jeff Elhai
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World Population
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Green Revolution
Conventional wheat
High yield dwarf wheat
NH3
NH3
www.Isuagcenter.com
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Chemical Fertilizer Production
100's of billions / year
N2
NH3
8 fold
Chemical production of NH3
Fixan PE, West FB (2002) Ambio 31169-176.
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Downstream effects of fertilizer runnoff
100's of billions / year
N2
NH3
Dead Zones
Low oxygen High oxygen
What to do?
NASA Visible Earth http//visibleearth.nasa.gov/
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Biological Fertilizer Production
100's of billions / year
N2
NH3

• Plant Symbiont

• Cyanobacterial Symbiont
• Nostoc punctiforme

N2
NH3
Anthoceros (bryophyte)
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Biological Fertilizer Production
100's of billions / year
N2
NH3

• Plant Symbiont

• Cyanobacterial Symbiont
• Nostoc punctiforme

N2
NH3
Cycads (gymnosperm)
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Biological Fertilizer Production
100's of billions / year
N2
NH3

• Plant Symbiont

• Cyanobacterial Symbiont
• Nostoc punctiforme

N2
NH3
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Biological Fertilizer Production
100's of billions / year
N2
NH3

• Cyanobacterial Symbiont
• Nostoc punctiforme

• But not

N2
NH3
Why not crop plants?
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How do symbiotic plants differ from others?
A clue from free-living Nostoc?
Starving for Nitrogen
Plenty of Nitrogen
NH3
NH3
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How does NH3 shut off N-fixation?
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How does NH3 shut off N-fixation?
a-ketoglutarate
Glutamine
Glutamate

Glutamate
AMINO ACIDS
N2
NH3
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How does NH3 shut off N-fixation?
a-ketoglutarate
Glutamine
Glutamate

Glutamate
AMINO ACIDS
N2
NH3
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How does NH3 shut off N-fixation?
Could plants use this to fool Nostoc?
a-ketoglutarate
Glutamine
Glutamate

Glutamate
AMINO ACIDS
N2
NH3
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How does NH3 shut off N-fixation?
Could plants use this to fool Nostoc?
a-ketoglutarate
Does Nostoc within plants have a high level of
a-ketoglutarate?
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How to measure a-ketoglutarate inside cells?
The hydromedusa Aequoria victoria Source of
GreenFluorescent Protein(GFP)
CyanoFluorescent Protein(CFP)
YellowFluorescent Protein(YFP)
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How to measure a-ketoglutarate inside cells?
The hydromedusa Aequoria victoria Source of
GreenFluorescent Protein(GFP)
CyanoFluorescent Protein(CFP)
YellowFluorescent Protein(YFP)
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How to measure a-ketoglutarate inside cells?
a-ketoglutarate
CFP
YFP
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How to measure a-ketoglutarate inside cells?
a-ketoglutarate
CFP
YFP
Yellow fluorescence
a-ketoglutarate
Blue fluorescence
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How to measure a-ketoglutarate inside cells?
a-ketoglutarate
CFP
YFP
Yellow fluorescence
a-ketoglutarate
Blue fluorescence
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How does NH3 shut off N-fixation?
Could plants use this to fool Nostoc?
a-ketoglutarate
Does Nostoc within plants have a high level of
a-ketoglutarate?
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How does NH3 shut off N-fixation?
Could crop plants do the same?
a-ketoglutarate
Does Nostoc within plants have a high level of
a-ketoglutarate?