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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