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Light PhysicsLight Physics

Solar EnergySolar Energy

Electromagnetic Electromagnetic SpectrumSpectrum

Electromagnetic Electromagnetic SpectrumSpectrum

StratosphereStratosphere–– 1350 W/m1350 W/m22

BiosphereBiosphere–– 1150 W/m1150 W/m22

2000 umol/m2000 umol/m22/s/s

1350 W/m2

1150 W/m2

Lecture 8Lecture 8PhotoregulationPhotoregulation

PhotosynthesisPhotosynthesis–– Light QuantityLight QuantityPhotomorphogenesisPhotomorphogenesis–– Light QualityLight QualityPhotoperiodismPhotoperiodism–– Light DurationLight DurationPhototropsimPhototropsim–– Light DirectionLight Direction

PhotoregulationPhotoregulation

PhotosynthesisPhotosynthesis–– PhotoreceptorsPhotoreceptors–– ChlorophyllsChlorophylls–– CarotenoidsCarotenoids

RegulationRegulation–– Photosynthetic EfficiencyPhotosynthetic Efficiency

High LightHigh LightLow LightLow Light

–– Emerson EnhancementEmerson Enhancement

ChlorophyllsChlorophylls

Phytol Chain

Chromophore

+ Protein

2

CarotenoidsCarotenoids

B-CAROTENE

Vitamin A Retinal

ABA(OH)

(OH)

Lutein

Light QualityLight Quality

Emerson Enhancement EffectEmerson Enhancement Effect

Copyright ©2006 by the National Academy of Sciences

Takahashi, Hiroko et al. (2006) Proc. Natl. Acad. Sci. USA 103, 477-482

Fig. 6. A proposed model for the migration of LHCII proteins during transition from state 1 to state 2

Photomorphogenesis Photomorphogenesis

Light QualityLight QualitySeed GerminationSeed Germination

Release from dormancyRelease from dormancyWeed seedsWeed seedsRed Light (5 sec) Induce GerminationRed Light (5 sec) Induce GerminationFarFar--Red (5 sec) Inhibit GerminationRed (5 sec) Inhibit Germination

R + FR R + FR -- InhibitInhibitR + FR + R R + FR + R -- InduceInduce

Seed GerminationSeed Germination

Dark 5’ Red

5’ R + 5’ FR R + FR + R

PhotomorphogenesisPhotomorphogenesis

Seedling DevelopmentSeedling DevelopmentEtiolatedEtiolated

DarkDarklong, spindly, white (or yellow)long, spindly, white (or yellow)

DeDe--EtiolatedEtiolatedLight Light Red Light ( 5 sec pulse)Red Light ( 5 sec pulse)

short, thick, greenshort, thick, greenR + FR R + FR etiolatedetiolated

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Seedling DevelopmentSeedling Development

MonocotDark

MonocotLight

DicotDark

DicotLight

Plastid DevelopmentPlastid Development

Gene ExpressionGene ExpressionNuclearNuclear

LHCII (Cab, LHCII (Cab, LhcbLhcb))rbcSrbcSPORPOR

PlastidPlastidpsaApsaA, , psbDpsbD, , rbcLrbcL

Plastid DevelopmentPlastid Development

ProplastidEarly Chloroplast Etioplast

PhotomorphogenesisPhotomorphogenesis

Internode ElongationInternode ElongationShade AdaptedShade Adapted (Shade Tolerant)(Shade Tolerant)

No ResponseNo ResponseShade AvoidanceShade Avoidance (Shade Sensitive)(Shade Sensitive)

Low Red : FarLow Red : Far--Red RatioRed RatioCanopy ShadeCanopy ShadeRapid ElongationRapid ElongationEscape ShadeEscape Shade

Shade AvoidanceShade Avoidance Photoperiodism Photoperiodism

DaylengthDaylength PerceptionPerceptionShortShort--Day PlantsDay PlantsDark Period Dark Period

Longer than Critical MinimumLonger than Critical Minimum5 min Night Break5 min Night Break

Red Red -- Inhibits FloweringInhibits FloweringFarFar--Red Red –– Promotes FloweringPromotes FloweringR + FR + R R + FR + R -- No FloweringNo Flowering

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Fig. 15-22, p. 253

long day,short night

short day,long night

short day,interrupted night

short day,red followedby far-red

short day,red interruption

white light

red light

red far-redflowers

flowers

Fig. 15-22, p. 253

long day,short night

short day,long night

short day,interrupted night

short day,red followedby far-red

short day,red interruption

white light

red light

red far-red

No flowers

No flowers

Fig. 15-22, p. 253

long day,short night

short day,long night

short day,interrupted night

short day,red followedby far-red

short day,red interruption

white light

red light

red far-red

No flowers

Phototropism Phototropism

Directional InformationDirectional InformationBlue LightBlue Light

Stem BendingStem BendingToward LightToward LightLateral Redistribution of Lateral Redistribution of AuxinAuxin

AuxinAuxin High on Shaded SideHigh on Shaded SideIncreased Growth Increased Growth

StomatalStomatal OpeningOpeningBlue Light Activation of ATPaseBlue Light Activation of ATPaseH+ ion extrusionH+ ion extrusionK+/K+/ClCl-- UptakeUptakeH2O uptakeH2O uptakeSwelling of Guard Cells Swelling of Guard Cells

PhototropismPhototropism PIN ComplexesPIN Complexes

StomatalStomatal OpeningOpening

DARK Light

PhotoreceptorsPhotoreceptors

1. 1. PhotosynthesisPhotosynthesisChlorophyllsChlorophyllsCarotenoidsCarotenoids

Energy Transfer Energy Transfer Light Light --------> Chemical Energy> Chemical Energy

2. 2. Photomorphogenesis & PhotoperiodismPhotomorphogenesis & PhotoperiodismRed / FarRed / Far--Red ReversibleRed ReversiblePhytochromePhytochrome

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PhotoreceptorsPhotoreceptors

3. Phototropism & 3. Phototropism & StomatalStomatal OpeningOpeningPhototropinPhototropin (Phot1, Phot2)(Phot1, Phot2)(Carotenoid?)(Carotenoid?)

4. Hypocotyl Elongation (Inhibition)4. Hypocotyl Elongation (Inhibition)CryptochromeCryptochrome (Cry1, Cry2, Cry3?)(Cry1, Cry2, Cry3?)

PhytochromePhytochrome

DarkDark RedRed DarkDarkP P -------------->Pr >Pr --------------------------------> > PfrPfr ------------> Response > Response

<<------------------------------FarFar--RedRed

Molecular Switch Molecular Switch PfrPfr -- Active FormActive Form

PhytochromePhytochrome AbsorptionAbsorptionPhotoequilibriumPhotoequilibrium ((Pfr/PtotPfr/Ptot))

PhytochromePhytochrome StructureStructure17.8 After synthesis and 17.8 After synthesis and assembly, assembly, phytochromephytochrome is is activated (Part 1)activated (Part 1)

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17.8 After synthesis and 17.8 After synthesis and assembly, assembly, phytochromephytochrome is is activated (Part 2)activated (Part 2)

17.14 Phytochrome 17.14 Phytochrome activity is modulated by activity is modulated by phosphorylation statusphosphorylation status

PhytochromePhytochrome GenesGenes

5 5 PhytochromePhytochrome GenesGenes1. 1. PhyAPhyA ------------> FR inhibition of Stem elongation> FR inhibition of Stem elongation

(etiolated plants) (etiolated plants) ----------> FR promotion of flowering> FR promotion of flowering

daylengthdaylength extensionextension

2. 2. PhyBPhyB ------------> R inhibition of Stem elongation> R inhibition of Stem elongation(etiolated plants) (etiolated plants)

----------> FR promotion of internode elongation> FR promotion of internode elongationshade avoidanceshade avoidance

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PhytochromePhytochrome GenesGenes

3. 3. PhyCPhyC ------------> ?> ?4. 4. PhyDPhyD ------------> ?> ?5. 5. PhyEPhyE ------------> ?> ?

Mechanism is still unclearMechanism is still unclear

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Blue LightBlue Light

CryptochromeCryptochrome–– CryCry--1, Cry1, Cry--2 2 –– Bacterial Bacterial PhotolyasesPhotolyases–– Hypocotyl Elongation (CryHypocotyl Elongation (Cry--1)1)–– Flowering (CryFlowering (Cry--2)2)PhototropinPhototropin–– PhotPhot--1, Phot1, Phot--22–– FlavoproteinsFlavoproteins–– Hypocotyl BendingHypocotyl BendingCarotenoidCarotenoid–– StomatalStomatal Opening (?)Opening (?)

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PhototropismPhototropism Blue Light Action Blue Light Action SpectrumSpectrum

Christie, J. M. et al. J. Biol. Chem. 2001;276:11457-11460

Physiological characteristics of cryptochrome and phototropin mutantsCryptochromeCryptochrome & & PhototropinPhototropin

Christie, J. M. et al. J. Biol. Chem. 2001;276:11457-11460

Protein structures of ECryptochromeCryptochrome & & PhototropinPhototropin

CryptochromeCryptochrome PhototropinPhototropin

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PhototropismPhototropism

PhototropinPhototropin MutantMutantFlavoproteinFlavoproteinLOV Domain + KinaseLOV Domain + Kinase–– 2 FMN Sites2 FMN SitesPlasma MembranePlasma Membrane–– PHOT 1PHOT 1

Low LightLow Light

–– PHOT 2PHOT 2High LightHigh Light

StomatalStomatal OpeningOpening

DARK Light

Blue Light ResponseBlue Light Response

PhotoreceptorPhotoreceptor

Carotenoid or Carotenoid or PhototropinPhototropin ??Evidence for BothEvidence for BothXanthophyllXanthophyll Cycle (Chloroplast)Cycle (Chloroplast)–– ViolaxanthinViolaxanthin

Light DarkLight Dark

–– ZeaxanthinZeaxanthin

PhototropinPhototropin (Plasma Membrane)(Plasma Membrane)

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UV Absorbing PigmentUV Absorbing Pigment

UVUV--B B (280(280--320 nm)320 nm)DNADNAThymidineThymidine DimersDimersChromosome DamageChromosome DamageUnknown PhotoreceptorUnknown Photoreceptor

UVUV--AA (320(320--400 nm)400 nm)ProteinProteinPhotolyasePhotolyaseDNA RepairDNA RepairPhototropinPhototropin