Light regulation of growth Plants sense 1 Light

Light regulation of growth Plants sense 1. Light quantity 2. Light quality (colors) 3. Light duration 4. Direction it comes from

Types of Phytochrome Responses Two categories based on speed 3 classes based on fluence (amount of light needed)

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 Light & TOC 1 activate LHY & CCA 1 at dawn LHY & CCA 1 repress TOC 1 in day, so they decline too At night TOC 1 is activated (not enough LHY & CCA 1) Phytochrome entrains the clock So does blue light

Blue Light Responses Circadian Rhythms

Blue Light Responses Circadian Rhythms Solar tracking

Blue Light Responses Circadian Rhythms Solar tracking Phototropism

Blue Light Responses Circadian Rhythms Solar tracking Phototropism Inhibiting stem elongation

Blue Light Responses Circadian Rhythms Solar tracking Phototropism Inhibiting stem elongation Chloroplast movement

Blue Light Responses Circadian Rhythms Solar tracking Phototropism Inhibiting stem elongation Chloroplast movement Stomatal opening

Blue Light Responses Circadian Rhythms Solar tracking Phototropism Inhibiting stem elongation Chloroplast movement Stomatal opening Gene expression

Blue Light Responses Circadian Rhythms Solar tracking Phototropism Inhibiting stem elongation Chloroplast movement Stomatal opening Gene expression Flowering in Arabidopsis

Blue Light Responses Circadian Rhythms Solar tracking Phototropism Inhibiting stem elongation Chloroplast movement Stomatal opening Gene expression Flowering in Arabidopsis Responses vary in their fluence requirements

Blue Light Responses Circadian Rhythms Solar tracking Phototropism Inhibiting stem elongation Chloroplast movement Stomatal opening Gene expression Flowering in Arabidopsis Responses vary in their fluence requirements & lag times

Blue Light Responses vary in their fluence requirements & lag time Stomatal opening is reversible by green light; others aren’t

Blue Light Responses vary in their fluence requirements & lag time Stomatal opening is reversible by green light; others aren’t Multiple blue receptors with different functions!

Blue Light Responses vary in their fluence requirements & lag time Stomatal opening is reversible by green light; others aren’t Multiple blue receptors with different functions! Identified by mutants

Blue Light Responses vary in their fluence requirements & lag time Stomatal opening is reversible by green light; others aren’t Multiple blue receptors with different functions! Identified by mutants, then clone the gene and identify the protein

Blue Light Responses vary in their fluence requirements & lag time Stomatal opening is reversible by green light; others aren’t Multiple blue receptors with different functions! Identified by mutants, then clone the gene and identify the protein Cryptochromes repress hypocotyl elongation

Blue Light Responses Cryptochromes repress hypocotyl elongation Stimulate flowering

Blue Light Responses Cryptochromes repress hypocotyl elongation Stimulate flowering Set the circadian clock (in humans, too!)

Blue Light Responses Cryptochromes repress hypocotyl elongation Stimulate flowering Set the circadian clock (in humans, too!) Stimulate anthocyanin synthesis

Blue Light Responses Cryptochromes repress hypocotyl elongation Stimulate flowering Set the circadian clock (in humans, too!) Stimulate anthocyanin synthesis 3 CRY genes

Blue Light Responses 3 CRY genes All have same basic structure: Photolyase-like domain binds FAD and a pterin (MTHF) that absorbs blue & transfers energy to FAD in photolyase (an enzyme that uses light energy to repair pyr dimers)

Blue Light Responses 3 CRY genes All have same basic structure: Photolyase-like domain binds FAD and a pterin (MTHF) that absorbs blue & transfers energy to FAD in photolyase (an enzyme that uses light energy to repair pyr dimers) DAS binds COP 1 & has nuclear localization signals

Blue Light Responses 3 CRY genes All have same basic structure: Photolyase-like domain binds FAD and a pterin (MTHF) that absorbs blue & transfers energy to FAD in photolyase (an enzyme that uses light energy to repair pyr dimers) DAS binds COP 1 & has nuclear localization signals CRY 1 & CRY 2 kinase proteins after absorbing blue

Blue Light Responses 3 CRY genes CRY 1 & CRY 2 kinase proteins after absorbing blue CRY 3 repairs mt & cp DNA!

Blue Light Responses 3 CRY genes 1. CRY 1 regulates blue effects on growth: light-stable • Triggers rapid changes in PM potential & growth

Blue Light Responses 3 CRY genes 1. CRY 1 regulates blue effects on growth: light-stable • Triggers rapid changes in PM potential & growth • Opens anion channels in PM

Blue Light Responses 3 CRY genes 1. CRY 1 regulates blue effects on growth: light-stable • Triggers rapid changes in PM potential & growth • Opens anion channels in PM • Stimulates anthocyanin synthesis

Blue Light Responses 3 CRY genes 1. CRY 1 regulates blue effects on growth: light-stable • Triggers rapid changes in PM potential & growth • Opens anion channels in PM • Stimulates anthocyanin synthesis • Entrains the circadian clock

Blue Light Responses 3 CRY genes 1. CRY 1 regulates blue effects on growth: light-stable • Triggers rapid changes in PM potential & growth • Opens anion channels in PM • Stimulates anthocyanin synthesis • Entrains the circadian clock • Also accumulates in nucleus & interacts with PHY & COP 1 to regulate photomorphogenesis, probably by kinasing substrates

Blue Light Responses 3 CRY genes 1. CRY 1 regulates blue effects on growth: light-stable • Triggers rapid changes in PM potential & growth • Opens anion channels in PM • Stimulates anthocyanin synthesis • Entrains the circadian clock • Also accumulates in nucleus & interacts with PHY & COP 1 to regulate photomorphogenesis, probably by kinasing substrates 2. CRY 2 controls flowering

Blue Light Responses 3 CRY genes 1. CRY 1 regulates blue effects on growth: light-stable 2. CRY 2 controls flowering: little effect on other processes • Light-labile

Blue Light Responses 3 CRY genes 1. CRY 1 regulates blue effects on growth: light-stable 2. CRY 2 controls flowering: little effect on other processes • Light-labile 3. CRY 3 enters cp & mito, where binds & repairs DNA!

Blue Light Responses 3 CRY genes 1. CRY 1 regulates blue effects on growth 2. CRY 2 controls flowering: little effect on other processes 3. CRY 3 enters cp & mito, where binds & repairs DNA! Cryptochromes are not involved in phototropism or stomatal opening!

Blue Light Responses Cryptochromes are not involved in phototropism or stomatal opening! Phototropins are!

Blue Light Responses Phototropins are involved in phototropism & stomatal opening! Many names (nph, phot, rpt) since found by several different mutant screens

Phototropins Many names (nph, phot, rpt) since found by several different mutant screens Mediate blue light-induced growth enhancements

Phototropins Many names (nph, phot, rpt) since found by several different mutant screens Mediate blue light-induced growth enhancement & blue light-dependent activation of the plasma membrane H+ATPase in guard cells

Phototropins Many names (nph, phot, rpt) since found by several different mutant screens Mediate blue light-induced growth enhancement & blue light-dependent activation of the plasma membrane H+ATPase in guard cells Contain light-activated serine-threonine kinase domain and LOV 1 (light-O 2 -voltage) and LOV 2 repeats

Phototropins Many names (nph, phot, rpt) since found by several different mutant screens Mediate blue light-induced growth enhancement & blue light-dependent activation of the plasma membrane H+ATPase in guard cells Contain light-activated serine-threonine kinase domain and LOV 1 (light-O 2 -voltage) and LOV 2 repeats LOV 1 & LOV 2 bind Flavin. Mono. Nucleotide cofactors

Phototropins Many names (nph, phot, rpt) since found by several different mutant screens Mediate blue light-induced growth enhancement & blue light-dependent activation of the plasma membrane H+ATPase in guard cells Contain light-activated serine-threonine kinase domain and LOV 1 (light-O 2 -voltage) and LOV 2 repeats LOV 1 & LOV 2 bind Flavin. Mono. Nucleotide cofactors After absorbing blue rapidly autophosphorylate & kinase other proteins

Phototropins After absorbing blue rapidly autophosphorylate & kinase other proteins 1 result = phototropism due to uneven auxin transport

Phototropins After absorbing blue rapidly autophosphorylate & kinase other proteins 1 result = phototropism due to uneven auxin transport Send more to side away from light!

Phototropins After absorbing blue rapidly autophosphorylate & kinase other proteins 1 result = phototropism due to uneven auxin transport Send more to side away from light! Phot 1 mediates LF

Phototropins After absorbing blue rapidly autophosphorylate & kinase other proteins 1 result = phototropism due to uneven auxin transport Send more to side away from light! PHOT 1 mediates LF PHOT 2 mediates HIR

Phototropins 2 nd result = stomatal opening via stimulation of guard cell PM proton pump Also requires photosynthesis by guard cells!

Phototropins 2 nd result = stomatal opening via stimulation of guard cell PM proton pump Also requires photosynthesis by guard cells & signaling from xanthophylls

Phototropins 2 nd result = stomatal opening via stimulation of guard cell PM proton pump Also requires photosynthesis by guard cells & signaling from xanthophylls npq mutants don’t make zeaxanthin & lack specific blue response

Phototropins 2 nd result = stomatal opening via stimulation of guard cell PM proton pump Also requires photosynthesis by guard cells & signaling from xanthophylls npq mutants don’t make zeaxanthin & lack specific blue response Basic idea: open when pump in K+

Phototropins 2 nd result = stomatal opening via stimulation of guard cell PM proton pump Also requires photosynthesis by guard cells & signaling from xanthophylls npq mutants don’t make zeaxanthin & lack specific blue response Basic idea: open when pump in K+ Close when pump out K+

Phototropins Basic idea: open when pump in K+ Close when pump out K+ Control is hideously complicated!

Phototropins Basic idea: open when pump in K+ Close when pump out K+ Control is hideously complicated! Mainly controlled by blue light

Phototropins Basic idea: open when pump in K+ Close when pump out K+ Control is hideously complicated! Mainly controlled by blue light, but red also plays role

Phototropins Basic idea: open when pump in K+ Close when pump out K+ Control is hideously complicated! Mainly controlled by blue light, but red also plays role Light intensity is also important

Phototropins Mainly controlled by blue light, but red also plays role Light intensity is also important due to effect on [photosynthate] in guard cells

Phototropins Mainly controlled by blue light, but red also plays role Light intensity is also important due to effect on [photosynthate] in guard cells PHOT 1 &2 also help

Phototropins Mainly controlled by blue light, but red also plays role Light intensity is also important due to effect on [photosynthate] in guard cells PHOT 1 &2 also help Main GC blue receptor is zeaxanthin!

Phototropins Mainly controlled by blue light, but red also plays role Light intensity is also important due to effect on [photosynthate] in guard cells PHOT 1 &2 also help Main GC blue receptor is zeaxanthin! Reason for green reversal

Phototropins Mainly controlled by blue light, but red also plays role Light intensity is also important due to effect on [photosynthate] in guard cells PHOT 1 &2 also help Main GC blue receptor is zeaxanthin! Reason for green reversal water stress overrides light!

Phototropins water stress overrides light: roots make Abscisic Acid: closes stomates & blocks opening regardless of other signals!

Plant Growth Size & shape depends on cell # & cell size Decide when, where and which way to divide

Plant Growth Size & shape depends on cell # & cell size Decide which way to divide & which way to elongate • Periclinal = perpendicular to surface

Plant Growth Size & shape depends on cell # & cell size Decide which way to divide & which way to elongate • Periclinal = perpendicular to surface: get longer

Plant Growth Size & shape depends on cell # & cell size Decide which way to divide & which way to elongate • Periclinal = perpendicular to surface: get longer • Anticlinal = parallel to surface

Plant Growth Size & shape depends on cell # & cell size Decide which way to divide & which way to elongate • Periclinal = perpendicular to surface: get longer • Anticlinal = parallel to surface: add more layers

Plant Growth Decide which way to divide & which way to elongate • Periclinal = perpendicular to surface: get longer • Anticlinal = parallel to surface: add more layers Now must decide which way to elongate

Plant Growth Decide which way to divide & which way to elongate • Periclinal = perpendicular to surface: get longer • Anticlinal = parallel to surface: add more layers Now must decide which way to elongate: which walls to stretch

Plant Cell Walls and Growth Carbohydrate barrier surrounding cell • Protects & gives cell shape

Plant Cell Walls and Growth Carbohydrate barrier surrounding cell • Protects & gives cell shape • 1˚ wall made first • mainly cellulose • Can stretch!

Plant Cell Walls and Growth Carbohydrate barrier surrounding cell • Protects & gives cell shape • 1˚ wall made first • mainly cellulose • Can stretch! • 2˚ wall made after growth stops • Lignins make it tough

Plant Cell Walls and Growth • 1˚ wall made first • mainly cellulose • Can stretch! Control elongation by controlling orientation of cell wall fibers as wall is made

Plant Cell Walls and Growth • 1˚ wall made first • mainly cellulose • Can stretch! Control elongation by controlling orientation of cell wall fibers as wall is made • 1˚ walls = 25% cellulose, 25% hemicellulose, 35% pectin, 5% protein (but highly variable)

Plant Cell Walls and Growth 1˚ walls = 25% cellulose, 25% hemicellulose, 35% pectin, 5% protein (but highly variable) Cellulose: ordered chains made of glucose linked b 1 -4

Plant Cell Walls and Growth 1˚ walls = 25% cellulose, 25% hemicellulose, 35% pectin, 5% protein (but highly variable) Cellulose: ordered chains made of glucose linked b 1 -4 • Cross-link with neighbors to form strong, stable fibers