Download Bio 226: Cell and Molecular Biology

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1. Arabidopsis
2. Fast plant
3. Sorghum
4. Brachypodium distachyon
5. Amaranthus (C4 dicot)
6. Quinoa
7. Kalanchoe
8. Venus fly traps
9. C3 vs C4 Atriplex
10. C3 vs C4 Flaveria
11. C3 vs C4 Panicum
12. P. oleracea C4-CAM
13. P. afra C3-CAM
14. M. crystallinum C3-CAM
Transition to Flowering
Adults are competent to flower, but need correct signals
Very complex process!
Can be affected by:
• Daylength
• T (esp Cold)
• Water stress
• Nutrition
• Hormones
• Age
Light regulation of Plant Development
•Germination
•Morphogenesis
•Sun/shade & shade avoidance
•Flowering
•Senescence
Light regulation of growth
Plants sense
1. Light quantity
2. Light quality (colors)
3. Light duration
4. Direction it comes from
Phytochrome
Darwin showed blue works best for phototropism
Red light (666 nm) promotes germination
Far red light (>700 nm) blocks germination
After alternate R/FR color of final flash decides outcome
Seeds don't want to germinate in the shade!
Pigment is
photoreversible
Phytochrome
Red light (666 nm) promotes germination
Far red light (730 nm) blocks germination
After alternate R/FR color of final flash decides outcome
Pigment is photoreversible! -> helped purify it!
Looked for pigment that absorbs first at 666 nm, then 730
Phytochrome
Red light (666 nm) promotes germination
Far red light (730 nm) blocks germination
After alternate R/FR color of final flash decides outcome
Pigment is photoreversible! -> helped purify it!
Looked for pigment that absorbs first at 666 nm, then 730
Phytochrome
Red light (666 nm) promotes germination
Far red light (730 nm) blocks germination
After alternate R/FR color of final flash decides outcome
Pigment is photoreversible! -> helped purify it!
Looked for pigment that absorbs first at 666 nm, then 730
Made as inactive cytoplasmic Pr that absorbs at 666 nm
Phytochrome
Made as inactive cytoplasmic Pr that absorbs at 666 nm or
in blue
Converts to active Pfr that absorbs far red (730nm)
Phytochrome
Made as inactive cytoplasmic Pr that absorbs at 666 nm or
in blue
Converts to active Pfr that absorbs far red (730nm)
97% of Pfr is converted back to Pr by far red light
Phytochrome
Made as inactive cytoplasmic Pr that absorbs at 666 nm or
in blue
Converts to active Pfr that absorbs far red (730nm)
97% of Pfr is converted back to Pr by far red light
Also slowly reverts in dark
Phytochrome
Made as inactive cytoplasmic Pr that absorbs at 666 nm or
in blue
Converts to active Pfr that absorbs far red (730nm)
97% of Pfr is converted back to Pr by far red light
Also slowly reverts in dark: how plants sense night length
Types of Phytochrome Responses
Two categories based on speed
1. Rapid biochemical events
2. Morphological changes
Types of Phytochrome Responses
Two categories based on speed
1. Rapid biochemical events
2. Morphological changes
Lag time also varies from minutes to weeks
Types of Phytochrome Responses
Two categories based on speed
1. Rapid biochemical events
2. Morphological changes
Lag time also varies from minutes to weeks: numbers of
steps after Pfr vary
Types of Phytochrome Responses
Lag time also varies from minutes to weeks: numbers of
steps after Pfr vary
"Escape time" until a response can no longer be reversed
by FR also varies
Types of Phytochrome Responses
Lag time also varies from minutes to weeks: numbers of
steps after Pfr vary
"Escape time" until a response can no longer be reversed
by FR also varies: time taken for Pfr to do its job
Conclusions: phytochrome acts on many processes in
many ways
Types of Phytochrome Responses
Two categories based on speed
3 classes based on fluence (amount of light needed)
1. VLF:induced by 0.1 nmol/m-2 , saturate @ 50nmol/m-2
Types of Phytochrome Responses
Two categories based on speed
3 classes based on fluence (amount of light needed)
1. VLF:induced by 0.1 nmol/m-2 , saturate @ 50nmol/m-2
• Changes 0.02% of Pr to Pfr
Types of Phytochrome Responses
3 classes based on fluence (amount of light needed)
1. VLF:induced by 0.1 nmol/m-2 , saturate @ 50nmol/m-2
• Changes 0.02% of Pr to Pfr
• Are not FR-reversible!
Types of Phytochrome Responses
3 classes based on fluence (amount of light needed)
1. VLF:induced by 0.1 nmol/m-2 , saturate @ 50nmol/m-2
• Changes 0.02% of Pr to Pfr
• Are not FR-reversible! But action spectrum same as Pr
Types of Phytochrome Responses
3 classes based on fluence (amount of light needed)
1. VLF:induced by 0.1 nmol/m-2 , saturate @ 50nmol/m-2
• Changes 0.02% of Pr to Pfr
• Are not FR-reversible! But action spectrum same as Pr
• Induced by FR!
Types of Phytochrome Responses
3 classes based on fluence (amount of light needed)
1. VLF:induced by 0.1 nmol/m-2 , saturate @ 50nmol/m-2
• Changes 0.02% of Pr to Pfr
• Are not FR-reversible! But action spectrum same as Pr
• Induced by FR!
Obey law of reciprocity:
1 nmol/m-2 x 100 s =
100 nmol/m-2 x 1 sec
Types of Phytochrome Responses
3 classes based on fluence (amount of light needed)
1. VLF:induced by 0.1 nmol/m-2 , saturate @ 50nmol/m-2
• Changes 0.02% of Pr to Pfr
• Are not FR-reversible! But action spectrum same as Pr
• Induced by FR!
Obey law of reciprocity:
1 nmol/m-2 x 100 s =
100 nmol/m-2 x 1 sec
Examples: Cab gene
induction, oat
coleoptile growth
Types of Phytochrome Responses
3 classes based on fluence (amount of light needed)
1. VLF:induced by 0.1 nmol/m-2 , saturate @ 50nmol/m-2
• Changes 0.02% of Pr to Pfr
• Are not FR-reversible! But action spectrum same as Pr
• Induced by FR!
Obey law of reciprocity:
1 nmol/m-2 x 100 s =
100 nmol/m-2 x 1 sec
Examples: Cab gene
induction, oat
coleoptile growth
2. LF: induced by
1 µmol/m-2, saturate @
1000 µmol/m-2
Types of Phytochrome Responses
3 classes based on fluence (amount of light needed)
1. VLF:induced by 0.1 nmol/m-2 , saturate @ 50nmol/m-2
2. LF: induced by 1 µmol/m-2, saturate @ 1000 µmol/m-2
Are FR-reversible!
Types of Phytochrome Responses
3 classes based on fluence (amount of light needed)
1. VLF:induced by 0.1 nmol/m-2 , saturate @ 50nmol/m-2
2. LF: induced by 1 µmol/m-2, saturate @ 1000 µmol/m-2
Are FR-reversible! Need > 3% Pfr
Types of Phytochrome Responses
3 classes based on fluence (amount of light needed)
1. VLF:induced by 0.1 nmol/m-2 , saturate @ 50nmol/m-2
2. LF: induced by 1 µmol/m-2, saturate @ 1000 µmol/m-2
Are FR-reversible! Need > 3% Pfr
Obey law of reciprocity
Types of Phytochrome Responses
3 classes based on fluence (amount of light needed)
1. VLF:induced by 0.1 nmol/m-2 , saturate @ 50nmol/m-2
2. LF: induced by 1 µmol/m-2, saturate @ 1000 µmol/m-2
Are FR-reversible! Need > 3% Pfr
Obey law of reciprocity
Examples : Lettuce seed
germination, mustard
photomorphogenesis,
inhibits flowering in SDP
Types of Phytochrome Responses
3 classes based on fluence (amount of light needed)
1. VLF:induced by 0.1 nmol/m-2 , saturate @ 50nmol/m-2
2. LF: induced by 1 µmol/m-2, saturate @ 1000 µmol/m-2
Are FR-reversible! Need > 3% Pfr
Obey law of reciprocity
Examples : Lettuce seed
Germination, mustard
photomorphogenesis,
inhibits flowering in SDP
3. HIR: require prolonged
exposure to higher fluence
Types of Phytochrome Responses
3 classes based on fluence (amount of light needed)
1. VLF:induced by 0.1 nmol/m-2 , saturate @ 50nmol/m-2
2. LF: induced by 1 µmol/m-2, saturate @ 1000 µmol/m-2
3. HIR: require prolonged exposure to higher fluence
Effect is proportional to
Fluence
Types of Phytochrome Responses
3 classes based on fluence (amount of light needed)
1. VLF:induced by 0.1 nmol/m-2 , saturate @ 50nmol/m-2
2. LF: induced by 1 µmol/m-2, saturate @ 1000 µmol/m-2
3. HIR: require prolonged exposure to higher fluence
Effect is proportional to
Fluence
Disobey law of reciprocity
Are not FR-reversible!
Types of Phytochrome Responses
3 classes based on fluence (amount of light needed)
1. VLF:induced by 0.1 nmol/m-2 , saturate @ 50nmol/m-2
2. LF: induced by 1 µmol/m-2, saturate @ 1000 µmol/m-2
3. HIR: require prolonged exposure to higher fluence
Effect is proportional to fluence
Disobey law of reciprocity
Are not FR-reversible!
Some are induced by FR!
Types of Phytochrome Responses
3 classes based on fluence (amount of light needed)
1. VLF:induced by 0.1 nmol/m-2 , saturate @ 50nmol/m-2
2. LF: induced by 1 µmol/m-2, saturate @ 1000 µmol/m-2
3. HIR: require prolonged exposure to higher fluence
Effect is proportional to fluence
Disobey law of reciprocity
Are not FR-reversible!
Some are induced by FR!
Examples: inhibition of
hypocotyl elongation in
many seedlings,
anthocyanin synthesis
Types of Phytochrome Responses
3 classes based on fluence (amount of light needed)
1. VLF:induced by 0.1 nmol/m-2 , saturate @ 50nmol/m-2
2. LF: induced by 1 µmol/m-2, saturate @ 1000 µmol/m-2
3. HIR: require prolonged exposure to higher fluence
Effect is proportional to fluence
Disobey law of reciprocity
Are not FR-reversible!
Some are induced by FR!
Examples: inhibition of
hypocotyl elongation in
many seedlings,
anthocyanin synthesis
Different responses =
Different phytochromes
Types of Phytochrome Responses
3 classes based on fluence (amount of light needed)
1. VLF:induced by 0.1 nmol/m-2 , saturate @ 50nmol/m-2
2. LF: induced by 1 µmol/m-2, saturate @ 1000 µmol/m-2
3. HIR: require prolonged exposure to higher fluence
Different responses = Different phytochromes:
3 in rice, 5 in Arabidopsis
Types of Phytochrome Responses
Different responses = Different phytochromes:
3 in rice, 5 in Arabidopsis
1. PHYA mediates VLF and HIR due to FR
Types of Phytochrome Responses
Different responses = Different phytochromes:
3 in rice, 5 in Arabidopsis
1. PHYA mediates VLF and HIR due to FR
• Very labile in light
Types of Phytochrome Responses
Different responses = Different phytochromes:
3 in rice, 5 in Arabidopsis
1. PHYA mediates VLF and HIR due to FR
• Very labile in light
2. PHYB mediates LF and HIR due to R
• Stable in light
Types of Phytochrome Responses
1. PHYA mediates VLF and HIR due to FR
• Very labile in light
2. PHYB mediates LF and HIR due to R
• Stable in light
3. Roles of PHYs C, D & E not so clear
PHYA & PHYB are often antagonistic.
Types of Phytochrome Responses
PHYA & PHYB are often antagonistic.
In sunlight PHYB mainly controls development
In shade PHYA 1st controls development, since FR is high
But PHYA is light-labile; PHYB takes over & stem grows
"shade-avoidance"
Phytochrome
Pr has cis-chromophore
Phytochrome
Pr has cis-chromophore
Red converts it to trans = active shape
Phytochrome
Pr has cis-chromophore
Red converts it to trans = active shape
Far-red reverts it to cis
Phytochrome
Pfr is a protein kinase: acts by kinasing key proteins
• some stays in cytoplasm & activates ion pumps
Phytochrome
Pfr is a protein kinase: acts by kinasing key proteins
• some stays in cytoplasm & activates ion pumps
• Rapid responses are due to changes in ion fluxes
Phytochrome
Pfr is a protein kinase: acts by kinasing key proteins
• some stays in cytoplasm & activates ion pumps
• Rapid responses are due to changes in ion fluxes
• Increase growth by activating PM H+ pump
Phytochrome
Pfr is a protein kinase: acts by kinasing key proteins
• some stay in cytoplasm & activate ion pumps
• Rapid responses are due to changes in ion fluxes
• most enter nucleus and kinase transcription factors
Phytochrome
Pfr is a protein kinase: acts by kinasing key proteins
• most enter nucleus and kinase transcription factors
• Lack NLS, nuclear import requires FHY1 and FHL
Phytochrome
Pfr is a protein kinase: acts by kinasing key proteins
• most enter nucleus and kinase transcription factors
• Lack NLS, nuclear import requires FHY1 and FHL
• Slow responses are due to changes in gene expression
Phytochrome
most enter nucleus and kinase transcription factors
• Slow responses are due to changes in gene expression
• Many targets of PHY are transcription factors, eg PIF3
Phytochrome
most enter nucleus and kinase transcription factors
• Slow responses are due to changes in gene expression
• Many targets of PHY are transcription factors, eg PIF3
• Activate cascades of genes for photomorphogenesis
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•
•
•
Phytochrome
Slow responses are due to changes in gene expression
Many targets of PHY are transcription factors, eg PIF3
Activate cascades of genes for photomorphogenesis
20% of genes are light-regulated
Phytochrome
• 20% of genes are light-regulated
• Protein degradation is important for light regulation
Phytochrome
• 20% of genes are light-regulated
• Protein degradation is important for light regulation
• Cop mutants are defective in specific types of protein
degradation
Phytochrome
• Protein degradation is important for light regulation
• Cop mutants are defective in specific types of protein
degradation
• COP1 helps target transcription factors for degradation
•
•
•
•
Phytochrome
Protein degradation is important for light regulation
Cop mutants are defective in specific types of protein
degradation
COP1 helps target transcription factors for degradation
W/O COP1 they act in dark
•
•
•
•
•
Phytochrome
Protein degradation is important for light regulation
Cop mutants are defective in specific types of protein
degradation
COP1 helps target transcription factors for degradation
W/O COP1 they act in dark
In light COP1 is exported to cytoplasm so TF can act
Phytochrome
• Protein degradation is important for light regulation
• Cop mutants are defective in specific types of protein
degradation
• COP1 helps target transcription factors for degradation
• W/O COP1 they act in dark
• In light COP1 is exported to cytoplasm so TF can act
• Other COPs are
part of protein
deg apparatus
(signalosome)
Other Phytochrome Responses
Circadian rhythms
• Many plant responses show circadian rhythms
Circadian rhythms
Many plant responses show circadian rhythms
Leaves move due to circadian ion fluxes in/out of dorsal &
ventral motor cells
Circadian rhythms
Many plant responses show circadian rhythms
• Once entrained, continue in constant dark
Circadian rhythms
Many plant responses show circadian rhythms
• Once entrained, continue in constant dark or light!
Circadian rhythms
Many plant responses show circadian rhythms
• Once entrained, continue in constant dark or light!
• Give plant headstart on photosynthesis, other processes
that need gene expression
Circadian rhythms
Many plant responses show circadian rhythms
• Once entrained, continue in constant dark or light!
• Give plant headstart on photosynthesis, other processes
that need gene expression
• Or elongate at night!
Circadian rhythms
Give plant headstart on photosynthesis, other processes
that need gene expression
• Or elongate at night!
• Endogenous oscillator is temperature-compensated, so
runs at same speed at all times
Circadian rhythms
Endogenous oscillator is temperature-compensated, so
runs at same speed at all times
• Is a negative feedback loop of transcription-translation
Circadian rhythms
Is a negative feedback loop of transcription-translation
• Light & TOC1 activate LHY & CCA1 at dawn
Circadian rhythms
Light & TOC1 activate LHY & CCA1 at dawn
LHY & CCA1 repress TOC1 in day, so they decline too
Circadian rhythms
Light & TOC1 activate LHY & CCA1 at dawn
LHY & CCA1 repress TOC1 in day, so they decline too
At night TOC1 is activated (not enough LHY & CCA1)
Circadian rhythms
Light & TOC1 activate LHY & CCA1 at dawn
LHY & CCA1 repress TOC1 in day, so they decline too
At night TOC1 is activated (not enough LHY & CCA1)
Phytochrome entrains the clock
Circadian rhythms
Light & TOC1 activate LHY & CCA1 at dawn
LHY & CCA1 repress TOC1 in day, so they decline too
At night TOC1 is activated (not enough LHY & CCA1)
Full story is far more complicated!
Circadian rhythms
Light & TOC1 activate LHY & CCA1 at dawn
LHY & CCA1 repress TOC1 in day, so they decline too
At night TOC1 is activated (not enough LHY & CCA1)
Phytochrome entrains the clock So does blue light