Transcript Document
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 & 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 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 Responses vary in their fluence requirements & lag time Stomatal opening is reversible by green light; others aren’t Blue Light Responses 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 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 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 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 COP1 & 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 COP1 & has nuclear localization signals CRY1 & CRY2 kinase proteins after absorbing blue Blue Light Responses 3 CRY genes CRY1 & CRY2 kinase proteins after absorbing blue CRY3 repairs mt & cp DNA! Blue Light Responses 3 CRY genes 1. CRY1 regulates blue effects on growth: light-stable • Triggers rapid changes in PM potential & growth Blue Light Responses 3 CRY genes 1. CRY1 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. CRY1 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. CRY1 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. CRY1 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 & COP1 to regulate photomorphogenesis, probably by kinasing substrates Blue Light Responses 3 CRY genes 1. CRY1 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 & COP1 to regulate photomorphogenesis, probably by kinasing substrates 2. CRY2 controls flowering Blue Light Responses 3 CRY genes 1. CRY1 regulates blue effects on growth: light-stable 2. CRY2 controls flowering: little effect on other processes • Light-labile Blue Light Responses 3 CRY genes 1. CRY1 regulates blue effects on growth: light-stable 2. CRY2 controls flowering: little effect on other processes • Light-labile 3. CRY3 enters cp & mito, where binds & repairs DNA! Blue Light Responses 3 CRY genes 1. CRY1 regulates blue effects on growth 2. CRY2 controls flowering: little effect on other processes 3. CRY3 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 LOV1 (light-O2-voltage) and LOV2 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 LOV1 (light-O2-voltage) and LOV2 repeats LOV1 & LOV2 bind FlavinMonoNucleotide 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 LOV1 (light-O2-voltage) and LOV2 repeats LOV1 & LOV2 bind FlavinMonoNucleotide 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 PHOT2 mediates HIR Phototropins 2nd result = stomatal opening via stimulation of guard cell PM proton pump Also requires photosynthesis by guard cells! Phototropins 2nd result = stomatal opening via stimulation of guard cell PM proton pump Also requires photosynthesis by guard cells & signaling from xanthophylls Phototropins 2nd 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 2nd 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 2nd 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 PHOT1 &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 PHOT1 &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 PHOT1 &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 PHOT1 &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