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Growth regulators Auxins Cytokinins Gibberellins Abscisic acid Ethylene Brassinosteroids All are small organics: made in one part, affect another part. Auxin signaling Auxin receptors eg TIR1 are E3 ubiquitin ligases ! - PowerPoint PPT Presentation
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Growth regulatorsAuxinsCytokininsGibberellinsAbscisic acidEthyleneBrassinosteroidsAll are small organics: made inone part, affectanother part
Auxin signalingAuxin receptors eg TIR1 are E3 ubiquitin ligases!Upon binding auxin they activate complexes targeting AUX/IAA proteins for degradation!AUX/IAA inhibit ARFtranscription factors,so this turns on "early genes"Some early genes turn on'late genes" needed for development
Auxin signalingABP1 is a different IAA receptor localized in ERActivates PM H+ pump by sending it to PM & keeping it thereDoes not affect gene expression!
Auxin & other growth regulatorsSome "late genes" synthesize ethylene (normally a wounding response): how 2,4-D kills?Auxin/cytokinin determines whether callus forms roots or shoots
CytokininsDiscovered as factors which induce cultured cells to divideHaberlandt (1913): phloem chemical stimulates division
CytokininsDiscovered as factors which induce cultured cells to divideHaberlandt (1913): phloem chemical stimulates divisionvan Overbeek (1941): coconut milk stimulates division
CytokininsDiscovered as factors which induce cultured cells to divideHaberlandt (1913): phloem chemical stimulates divisionvan Overbeek (1941): coconut milk stimulates divisionMiller Skoog (1955): degraded DNA stimulates division!
CytokininsDiscovered as factors which induce cultured cells to divideHaberlandt (1913): phloem chemical stimulates division van Overbeek (1941): coconut milk stimulates divisionMiller Skoog (1955): degraded DNA stimulates division!Kinetin was the breakdown product
CytokininsDiscovered as factors which induce cultured cells to divideHaberlandt (1913): phloem chemical stimulates division van Overbeek (1941): coconut milk stimulates divisionMiller Skoog (1955): degraded DNA stimulates division!Kinetin was the breakdown productDerived from adenine
CytokininsDiscovered as factors which induce cultured cells to divideHaberlandt (1913): phloem chemical stimulates division van Overbeek (1941): coconut milk stimulates divisionMiller Skoog (1955): degraded DNA stimulates division!Kinetin was the breakdown productDerived from adenineRequires auxin to stimulate division
CytokininsRequires auxin to stimulate divisionKinetin/auxin determines tissue formed (original fig)
CytokininsRequires auxin to stimulate divisionKinetin/auxin determines tissue formedInspired search for natural cytokininsMiller& Letham (1961) simultaneously found zeatin in cornKinetin trans- Zeatin
CytokininsMiller& Letham (1961) simultaneously found zeatinLater found in many spp including coconut milk
Kinetin trans-Zeatin
CytokininsMiller& Letham (1961) simultaneously found zeatinLater found in many spp including coconut milkTrans form is more active,but both exist (& work)Many other natural & synthetics have been identified
CytokininsMany other natural & synthetics have been identifiedLike auxins, many are bound to sugars or nucleotides
CytokininsMany other natural & synthetics have been identifiedLike auxins, many are bound to sugars or nucleotidesInactive, but easily converted
Cytokinin SynthesisMost cytokinins are made at root apical meristem & transported to sinks in xylem
Cytokinin SynthesisMost cytokinins are made at root apical meristem & transported to sinks in xylemTherefore have inverse gradientwith IAA
Cytokinin SynthesisMost cytokinins are made at root apical meristem & transported to sinks in xylemTherefore have inverse gradientwith IAAWhy IAA/CK affects development
Cytokinin SynthesisMost cytokinins are made at root apical meristem & transported to sinks in xylemTherefore have inverse gradientwith IAAWhy IAA/CK affects developmentRapidly metabolized by sink
Cytokinin EffectsRegulate cell divisionNeed mutants defective in CK metabolism or signaling to detect this in vivo
Cytokinin EffectsRegulate cell divisionNeed mutants defective in CK metabolism or signaling to detect this in vivoSAM & plants are smaller when[CK]
Cytokinin EffectsSAM & plants are smaller when [CK]Roots are longer!
Cytokinin EffectsUsually roots have too much CK: inhibits division! Cytokinins mainly act @ root & shoot meristems
Cytokinin EffectsCytokinins mainly act @ root & shoot meristemsControl G1-> S & G2-> M transition
Cytokinin EffectsPromote lateral bud growth
Cytokinin EffectsPromote lateral bud growthDelay leaf senescence
Cytokinin EffectsPromote lateral bud growthDelay leaf senescencePromote cp development, even in dark
Cytokinin ReceptorsReceptors were identified by mutationResemble bacterial 2-component signaling systems
Cytokinin Action1.Cytokinin binds receptor's extracellular domain
Cytokinin Action1.Cytokinin binds receptor's extracellular domain2. Activated protein kinases His kinase & receiver domains
Cytokinin Action1.Cytokinin binds receptor's extracellular domain2. Activated protein kinases His kinase & receiver domains3. Receiver kinases His-P transfer relay protein (AHP)
Cytokinin Action1.Cytokinin binds receptor's extracellular domain2. Activated protein kinases His kinase & receiver domains3. Receiver kinases His-P transfer relay protein (AHP)4. AHP-P enters nucleus & kinases ARR response regulators
Cytokinin Action4. AHP-P enters nucleus & kinases ARR response regulators5. Type B ARR induce type A
Cytokinin Action4. AHP-P enters nucleus & kinases ARR response regulators5. Type B ARR induce type A6. Type A create cytokininresponses
Cytokinin Action4. AHP-P enters nucleus & kinases ARR response regulators5. Type B ARR induce type A6. Type A create cytokininresponses 7. Most other effectors are unknownbut D cyclins is one effect.
Auxin & other growth regulatorsSome "late genes" synthesize ethylene (normally a wounding response): how 2,4-D kills?Auxin/cytokinin determines whether callus forms roots or shoots Auxin induces Gibberellins
GibberellinsDiscovered by studying "foolish seedling" disease in riceHori (1898): caused by a fungus
GibberellinsDiscovered by studying "foolish seedling" disease in riceHori (1898): caused by a fungusSawada (1912): growth is caused by fungal stimulus
GibberellinsDiscovered by studying "foolish seedling" disease in riceHori (1898): caused by a fungusSawada (1912): growth is caused by fungal stimulusKurosawa (1926): fungal filtrate causes these effects
GibberellinsDiscovered by studying "foolish seedling" disease in riceKurosawa (1926): fungal filtrate causes these effectsYabuta (1935): purified gibberellins from filtrates of Gibberella fujikuroi cultures
GibberellinsDiscovered by studying "foolish seedling" disease in riceKurosawa (1926): fungal filtrate causes these effectsYabuta (1935): purified gibberellins from filtrates of Gibberella fujikuroi cultures Discovered in plants in 1950s
GibberellinsDiscovered in plants in 1950s"rescued" some dwarf corn & pea mutants
GibberellinsDiscovered in plants in 1950s"rescued" some dwarf corn & pea mutantsMade rosette plants bolt
GibberellinsDiscovered in plants in 1950s"rescued" some dwarf corn & pea mutantsMade rosette plants boltTrigger adulthood in ivy & conifers
Gibberellins"rescued" some dwarf corn & pea mutantsMade rosette plants boltTrigger adulthood in ivy & conifersInduce growth of seedless fruit
Gibberellins"rescued" some dwarf corn & pea mutantsMade rosette plants boltTrigger adulthood in ivy & conifersInduce growth of seedless fruitPromote seed germination
Gibberellins"rescued" some dwarf corn & pea mutantsMade rosette plants boltTrigger adulthood in ivy & conifersInduce growth of seedless fruitPromote seed germinationInhibitors shorten stems: prevent lodging
Gibberellins"rescued" some dwarf corn & pea mutantsMade rosette plants boltTrigger adulthood in ivy & conifersInduce growth of seedless fruitPromote seed germinationInhibitors shorten stems: prevent lodging>136 gibberellins (based on structure)!
Gibberellins>136 gibberellins (based on structure)!Most plants have >10
Gibberellins>136 gibberellins (based on structure)!Most plants have >10Activity varies dramatically!
Gibberellins>136 gibberellins (based on structure)!Most plants have >10Activity varies dramatically!Most are precursors or degradation products
Gibberellins>136 gibberellins (based on structure)!Most plants have >10Activity varies dramatically!Most are precursors or degradation productsGAs 1, 3 & 4 are most bioactive
Gibberellin signalingUsed mutants to learn about GA signaling
Gibberellin signalingUsed mutants to learn about GA signalingMany are involved in GA synthesis
Gibberellin signalingUsed mutants to learn about GA signalingMany are involved in GA synthesisVaries during development
Gibberellin signalingUsed mutants to learn about GA signalingMany are involved in GA synthesisVaries during developmentOthers hit GA signalingGid = GA insensitive
Gibberellin signalingUsed mutants to learn about GA signalingMany are involved in GA synthesisVaries during developmentOthers hit GA signalingGid = GA insensitive encode GA receptors
Gibberellin signalingUsed mutants to learn about GA signalingMany are involved in GA synthesisVaries during developmentOthers hit GA signalingGid = GA insensitive encode GA receptorsSly = E3 receptors
Gibberellin signalingUsed mutants to learn about GA signalingMany are involved in GA synthesisVaries during developmentOthers hit GA signalingGid = GA insensitive encode GA receptorsSly = E3 receptorsDELLA (eg rga) = repressors of GA signaling
GibberellinsGAs 1, 3 & 4 are most bioactiveAct by triggering degradationof DELLA repressors
GibberellinsGAs 1, 3 & 4 are most bioactiveMade at many locations in plantAct by triggering degradationof DELLA repressorsw/o GA DELLA binds & blocks activator (GRAS)
GibberellinsAct by triggering degradation of DELLA repressorsw/o GA DELLA binds & blocks activatorbioactive GA binds GID1; GA-GID1 binds DELLA & marks for destruction
GibberellinsAct by triggering degradation of DELLA repressorsw/o GA DELLA binds & blocks activatorbioactive GA binds GID1; GA-GID1 binds DELLA & marks for destructionGA early genes are transcribed, start GA responses
Gibberellins & barley germinationGA made by embryo diffuse to aleurone & trigger events leading to germination
GA & stem elongationGA increase elongation, but lag >>> IAA
GA & stem elongationGA increase elongation, but lag >>> IAAIncrease cell wall creepage, but don't change pH (much)
GA & stem elongationGA increase elongation, but lag >>> IAAIncrease cell wall creepage, but don't change pH (much)Part of effect is increased expansin gene expression
GA & stem elongationGA increase elongation, but lag >>> IAAIncrease cell wall creepage, but don't change pH (much)Part of effect is increased expansin gene expressionAnother part is increasedcell division
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