Plant Growth & Development 3 stages Embryogenesis Fertilization to seed 2. Vegetative growth Juvenile stage Germination to adult "phase change" marks transition 3. Reproductive development Make flowers, can reproduce sexually

Light regulation of growth Plants sense Light quantity Light quality (colors) Light duration Direction it comes from

Light regulation of growth Measures night! 30" flashes during night stop flowers LDP plants such as Arabidopsis need long days to flower SDP flower in fall, LDP flower in spring, neutral flower when ready Next : color matters! Red light works best for flowering

Phytochrome Next : color matters! Red light (666 nm)works best for flowering & for germination of many seeds! But, Darwin showed blue works best for phototropism!

Phytochrome But, Darwin showed blue works best for phototropism! Different photoreceptor! Red light (666 nm) promotes germination Far red light (>700 nm) blocks germination

Phytochrome 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 Rapid biochemical events Morphological changes

Types of Phytochrome Responses Two categories based on speed Rapid biochemical events Morphological changes Lag time also varies from minutes to weeks

Types of Phytochrome Responses Two categories based on speed Rapid biochemical events 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) 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) 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) 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) 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) 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) 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) 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) 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) 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) 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) 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) 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) 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) 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) 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) 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) 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) 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) 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 PHYA mediates VLF and HIR due to FR

Types of Phytochrome Responses Different responses = Different phytochromes: 3 in rice, 5 in Arabidopsis 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 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 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

Types of Phytochrome Responses 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

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

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 some stay in cytoplasm & activate ion pumps Rapid responses are due to changes in ion fluxes most enter nucleus and kinase transcription factors 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

Phytochrome Slow responses are due to changes in gene expression Many targets of PHY are transcription factors, eg PIF3 Activate cascades of genes for light responses Some overlap, and some are unique to each phy

Phytochrome Slow responses are due to changes in gene expression Many targets of PHY are transcription factors, eg PIF3 Activate cascades of genes for light responses Some overlap, and some are unique to each phy 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 can’t degrade specific proteins

Phytochrome Protein degradation is important for light regulation Cop mutants can’t degrade specific proteins COP1/SPA targets specific transcription factors for degradation

Phytochrome Protein degradation is important for light regulation Cop mutants can’t degrade specific proteins COP1/SPA targets specific TF for degradation DDA1/DET1/COP10 target other proteins for degradation

Phytochrome Protein degradation is important for light regulation Cop mutants can’t degrade specific proteins COP1/SPA targets specific TF for degradation DDA1/DET1/COP10 target other proteins for degradation Other COPs form part of COP9 signalosome

Phytochrome Protein degradation is important for light regulation Cop mutants can’t degrade specific proteins COP1/SPA targets specific TF for degradation DDA1/DET1/COP10 target other proteins Other COPs form part of COP9 signalosome W/O COPs these TF act in dark

Phytochrome COPs target specific TF for degradation W/O COPs they act in dark In light COP1 is exported to cytoplasm so TF can act Tags PHYA by itself on the way out!

Other Phytochrome Responses In shade avoidance FR stimulates IAA synthesis from trp! Occurs in < 1 hour

Other Phytochrome Responses In shade avoidance FR stimulates IAA synthesis from trp! Occurs in < 1 hour Also occurs in response to endogenous ethylene!

Other Phytochrome Responses Flowering under short days is controlled via protein deg COP & CUL4 mutants flower early

Other Phytochrome Responses Flowering under short days is controlled via protein deg COP & CUL4 mutants flower early Accumulate FT (Flowering locus T) mRNA early FT mRNA abundance shows strong circadian rhythm

Other Phytochrome Responses Circadian rhythms Many plant responses, some developmental, some physiological, show circadian rhythms

Circadian rhythms Many plant responses, some developmental, some physiological, 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! Gives 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! Gives plant headstart on photosynthesis, other processes that need gene expression eg elongation at night!

Circadian rhythms Gives plant headstart on photosynthesis, other processes that need gene expression eg 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 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) Phytochrome entrains the clock So does blue light