Growth regulators All are small organics: made in one part, affect another part Treating a plant tissue with a hormone is like putting a dime in a vending machine. It depends on the machine, not the dime!

Auxin signaling Used "auxin-resistant" mutants to find genes involved in auxin signaling Many are involved in selective protein degradation! Some auxin receptors, eg TIR1 are E3 ubiquitin ligases!

Auxin signaling Some auxin receptors eg TIR1 are E3 ubiquitin ligases! Upon binding auxin they activate complexes targeting AUX/IAA proteins for degradation! AUX/IAA inhibit ARF transcription factors, so this turns on "early genes"

Auxin signaling Auxin receptors eg TIR1 are E3 ubiquitin ligases! Upon binding auxin they activate complexes targeting AUX/IAA proteins for degradation! AUX/IAA inhibit ARF transcription factors, so this turns on "early genes" Some early genes turn on 'late genes" needed for development

Auxin signaling ABP1 is a different IAA receptor localized in ER Activates PM H+ pump by sending it to PM & keeping it there

Auxin signaling ABP1 is a different IAA receptor localized in ER Activates PM H+ pump by sending it to PM & keeping it there Does not affect gene expression!

Auxin & other growth regulators ABP1 is a different IAA receptor localized in ER Stimulates PM H+ pump by sending it to PM & keeping it there. Does not affect gene expression! Some "late genes" synthesize ethylene (normally a wounding response): how 2,4-D kills?

Auxin & other growth regulators Some "late genes" synthesize ethylene (normally a wounding response): how 2,4-D kills? Auxin/cytokinin determines whether callus forms roots or shoots

Cytokinins Discovered as factors which induce cultured cells to divide Haberlandt (1913): phloem chemical stimulates division

Cytokinins Discovered as factors which induce cultured cells to divide Haberlandt (1913): phloem chemical stimulates division van Overbeek (1941): coconut milk stimulates division

Cytokinins Discovered as factors which induce cultured cells to divide Haberlandt (1913): phloem chemical stimulates division van Overbeek (1941): coconut milk stimulates division Miller… Skoog (1955): degraded DNA stimulates division!

Cytokinins Discovered as factors which induce cultured cells to divide Haberlandt (1913): phloem chemical stimulates division van Overbeek (1941): coconut milk stimulates division Miller… Skoog (1955): degraded DNA stimulates division! Kinetin was the breakdown product

Cytokinins Discovered as factors which induce cultured cells to divide Haberlandt (1913): phloem chemical stimulates division van Overbeek (1941): coconut milk stimulates division Miller… Skoog (1955): degraded DNA stimulates division! Kinetin was the breakdown product Derived from adenine

Cytokinins Discovered as factors which induce cultured cells to divide Haberlandt (1913): phloem chemical stimulates division van Overbeek (1941): coconut milk stimulates division Miller… Skoog (1955): degraded DNA stimulates division! Kinetin was the breakdown product Derived from adenine Requires auxin to stimulate division

Cytokinins Requires auxin to stimulate division Kinetin/auxin determines tissue formed (original fig)

Cytokinins Requires auxin to stimulate division Kinetin/auxin determines tissue formed Inspired search for natural cytokinins Miller& Letham (1961) ± simultaneously found zeatin in corn Kinetin trans- Zeatin

Cytokinins Miller& Letham (1961) ± simultaneously found zeatin Later found in many spp including coconut milk Kinetin trans-Zeatin

Cytokinins Miller& Letham (1961) ± simultaneously found zeatin Later found in many spp including coconut milk Trans form is more active, but both exist (& work) Many other natural & synthetics have been identified

Cytokinins Many other natural & synthetics have been identified Like auxins, many are bound to sugars or nucleotides

Cytokinins Many other natural & synthetics have been identified Like auxins, many are bound to sugars or nucleotides Inactive, but easily converted

Cytokinin Synthesis Most cytokinins are made at root apical meristem & transported to sinks in xylem

Cytokinin Synthesis Most cytokinins are made at root apical meristem & transported to sinks in xylem Therefore have inverse gradient with IAA

Cytokinin Synthesis Most cytokinins are made at root apical meristem & transported to sinks in xylem Therefore have inverse gradient with IAA Why IAA/CK affects development

Cytokinin Synthesis Most cytokinins are made at root apical meristem & transported to sinks in xylem Therefore have inverse gradient with IAA Why IAA/CK affects development Rapidly metabolized by sink

Cytokinin Effects Regulate cell division Need mutants defective in CK metabolism or signaling to detect this in vivo

Cytokinin Effects Regulate cell division Need mutants defective in CK metabolism or signaling to detect this in vivo SAM & plants are smaller when [CK]

Cytokinin Effects SAM & plants are smaller when [CK] Roots are longer!

Cytokinin Effects Usually roots have too much CK: inhibits division! Cytokinins mainly act @ root & shoot meristems

Cytokinin Effects Cytokinins mainly act @ root & shoot meristems Control G1-> S & G2-> M transition

Cytokinin Effects Promote lateral bud growth

Cytokinin Effects Promote lateral bud growth Delay leaf senescence

Cytokinin Effects Promote lateral bud growth Delay leaf senescence Promote cp development, even in dark

Cytokinin Receptors Receptors were identified by mutation Resemble bacterial 2-component signaling systems

Cytokinin Action 1.Cytokinin binds receptor's extracellular domain

Cytokinin Action 1.Cytokinin binds receptor's extracellular domain 2. Activated protein kinases His kinase & receiver domains

Cytokinin Action 1.Cytokinin binds receptor's extracellular domain 2. Activated protein kinases His kinase & receiver domains 3. Receiver kinases His-P transfer relay protein (AHP)

Cytokinin Action 1.Cytokinin binds receptor's extracellular domain 2. Activated protein kinases His kinase & receiver domains 3. Receiver kinases His-P transfer relay protein (AHP) 4. AHP-P enters nucleus & kinases ARR response regulators

Cytokinin Action 4. AHP-P enters nucleus & kinases ARR response regulators 5. Type B ARR induce type A

Cytokinin Action 4. AHP-P enters nucleus & kinases ARR response regulators 5. Type B ARR induce type A 6. Type A create cytokinin responses

Cytokinin Action 4. AHP-P enters nucleus & kinases ARR response regulators 5. Type B ARR induce type A 6. Type A create cytokinin responses 7. Most other effectors are unknown but D cyclins is one effect.

Auxin & other growth regulators Some "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

Gibberellins Discovered by studying "foolish seedling" disease in rice Hori (1898): caused by a fungus

Gibberellins Discovered by studying "foolish seedling" disease in rice Hori (1898): caused by a fungus Sawada (1912): growth is caused by fungal stimulus

Gibberellins Discovered by studying "foolish seedling" disease in rice Hori (1898): caused by a fungus Sawada (1912): growth is caused by fungal stimulus Kurosawa (1926): fungal filtrate causes these effects

Gibberellins Discovered by studying "foolish seedling" disease in rice Kurosawa (1926): fungal filtrate causes these effects Yabuta (1935): purified gibberellins from filtrates of Gibberella fujikuroi cultures

Gibberellins Discovered by studying "foolish seedling" disease in rice Kurosawa (1926): fungal filtrate causes these effects Yabuta (1935): purified gibberellins from filtrates of Gibberella fujikuroi cultures Discovered in plants in 1950s

Gibberellins Discovered in plants in 1950s "rescued" some dwarf corn & pea mutants

Gibberellins Discovered in plants in 1950s "rescued" some dwarf corn & pea mutants Made rosette plants bolt

Gibberellins Discovered in plants in 1950s "rescued" some dwarf corn & pea mutants Made rosette plants bolt Trigger adulthood in ivy & conifers

Gibberellins "rescued" some dwarf corn & pea mutants Made rosette plants bolt Trigger adulthood in ivy & conifers Induce growth of seedless fruit

Gibberellins "rescued" some dwarf corn & pea mutants Made rosette plants bolt Trigger adulthood in ivy & conifers Induce growth of seedless fruit Promote seed germination

Gibberellins "rescued" some dwarf corn & pea mutants Made rosette plants bolt Trigger adulthood in ivy & conifers Induce growth of seedless fruit Promote seed germination Inhibitors shorten stems: prevent lodging

Gibberellins "rescued" some dwarf corn & pea mutants Made rosette plants bolt Trigger adulthood in ivy & conifers Induce growth of seedless fruit Promote seed germination Inhibitors 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 >10 Activity varies dramatically!

Gibberellins >136 gibberellins (based on structure)! Most plants have >10 Activity varies dramatically! Most are precursors or degradation products

Gibberellins >136 gibberellins (based on structure)! Most plants have >10 Activity varies dramatically! Most are precursors or degradation products GAs 1, 3 & 4 are most bioactive

Gibberellin signaling Used mutants to learn about GA signaling

Gibberellin signaling Used mutants to learn about GA signaling Many are involved in GA synthesis

Gibberellin signaling Used mutants to learn about GA signaling Many are involved in GA synthesis Varies during development

Gibberellin signaling Used mutants to learn about GA signaling Many are involved in GA synthesis Varies during development Others hit GA signaling Gid = GA insensitive

Gibberellin signaling Used mutants to learn about GA signaling Many are involved in GA synthesis Varies during development Others hit GA signaling Gid = GA insensitive encode GA receptors

Gibberellin signaling Used mutants to learn about GA signaling Many are involved in GA synthesis Varies during development Others hit GA signaling Gid = GA insensitive encode GA receptors Sly = E3 receptors 63

Gibberellin signaling Used mutants to learn about GA signaling Many are involved in GA synthesis Varies during development Others hit GA signaling Gid = GA insensitive encode GA receptors Sly = E3 receptors DELLA (eg rga) = repressors of GA signaling

Gibberellins GAs 1, 3 & 4 are most bioactive Act by triggering degradation of DELLA repressors

Gibberellins GAs 1, 3 & 4 are most bioactive Made at many locations in plant Act by triggering degradation of DELLA repressors w/o GA DELLA binds & blocks activator (GRAS)

Gibberellins Act by triggering degradation of DELLA repressors w/o GA DELLA binds & blocks activator bioactive GA binds GID1; GA-GID1 binds DELLA & marks for destruction

Gibberellins Act by triggering degradation of DELLA repressors w/o GA DELLA binds & blocks activator bioactive GA binds GID1; GA-GID1 binds DELLA & marks for destruction GA early genes are transcribed, start GA responses

Gibberellins & barley germination GA made by embryo diffuse to aleurone & trigger events leading to germination

GA & stem elongation GA increase elongation, but lag >>> IAA

GA & stem elongation GA increase elongation, but lag >>> IAA Increase cell wall creepage, but don't change pH (much)

GA & stem elongation GA increase elongation, but lag >>> IAA Increase cell wall creepage, but don't change pH (much) Part of effect is increased expansin gene expression

GA & stem elongation GA increase elongation, but lag >>> IAA Increase cell wall creepage, but don't change pH (much) Part of effect is increased expansin gene expression Another part is increased cell division

GA & other hormones GA interacts w many other hormones t/o plant life cycle

GA & other hormones GA interacts w many other hormones t/o plant life cycle + with auxin via DELLA & induction of GA synthesis

GA & other hormones GA interacts w many other hormones t/o plant life cycle + with auxin via DELLA & induction of GA synthesis with cytokinins via reciprocal effects on synthesis

GA & other hormones GA interacts w many other hormones t/o plant life cycle + with auxin via DELLA & induction of GA synthesis - with cytokinins via reciprocal effects on synthesis - with ABA via Myb & DELLA

ABA Discovered as inhibitor of auxin –induced elongation (inhibitor b). Also found lots in tissues going dormant (dormin) Also found chemicals from senescing leaves & fruits that accelerated leaf abscission (abscission II) Was abscisic acid

ABA Counteracts GA effects Causes seed dormancy & inhibits seed germination Inhibits fruit ripening

ABA Also made in response to many stresses. Most is made in root & transported to shoot

ABA Most is made in root & transported to shoot in response to stress Closes stomates by opening Ca then closing K channels

ABA Synthesized during seed maturation to promote dormancy Also closes stomates in stress by opening Ca then closing K channels Induces many genes (~10% of total) via several different mechs bZIP/ABRE (ABI3, 4, 5 + AREBs)

ABA Synthesized during seed maturation to promote dormancy Also closes stomates in stress by opening Ca then closing K channels Induces many genes (~10% of total) via several different mechs bZIP/ABRE (ABI3, 4, 5 + AREBs) MYC/MYB

ABA Induces many genes (~10% of total) via several different mechs bZIP/ABRE (ABI3, 4, 5 + AREBs) MYC/MYB Jae-Hoon Lee has found 3 DWA genes that mark ABI5 (but not MYC or MYB) for destruction

TAIZ-Zeiger version of ABA signaling 3 groups of receptors GTG in PM Resemble GPCR

TAIZ-Zeiger version of ABA signaling 3 groups of receptors GTG in PM Resemble GPCR IP3 has role in ABA Unclear if GTG cause IP3 production

TAIZ-Zeiger version of ABA signaling 3 groups of receptors GTG in PM CHLH in Cp Also catalyzes Chl synthesis

TAIZ-Zeiger version of ABA signaling 3 groups of receptors GTG in PM CHLH in Cp Also catalyzes Chl synthesis And signals cp damage to nucleus

TAIZ-Zeiger version of ABA signaling 3 groups of receptors GTG in PM CHLH in Cp PYR/PYL/RCAR cytoplasmic

Schroeder version of ABA signaling PYR/PYL/RCAR is key player Binds ABA& inactivates PP2C

Schroeder version of ABA signaling PYR/PYL/RCAR is key player Binds ABA& inactivates PP2C Allows SnRK2 to function

Schroeder version of ABA signaling PYR/PYL/RCAR is key player Binds ABA& inactivates PP2C Allows SnRK2 to function SnRK2 then kinases many targets, including ion channels, TFs & ROS producers

ABA signaling in Guard Cells

Ethylene A gas that acts as a hormone! Chinese burned incense to ripen pears 1864: leaks from street lamps damage trees Neljubow (1901): ethylene causes triple response: short stems, swelling & abnormal horizontal growth

Ethylene A gas that acts as a hormone! Chinese burned incense to ripen pears 1864: leaks from street lamps damage trees Neljubow (1901): ethylene causes triple response: short stems, swelling & abnormal horizontal growth Doubt (1917): stimulates abscission Gane (1934): a natural plant product

Ethylene Effects Climacteric fruits produce spike of ethylene at start of ripening & exogenous ethylene enhances this

Ethylene Effects Climacteric fruits produce spike of ethylene at start of ripening & exogenous ethylene enhances this Results: 1) increased respiration 2) production of hydrolases & other enzymes involved in ripening

Ethylene Effects Normally IAA from leaf tip keeps abscission zone healthy

Ethylene Effects Normally IAA from leaf tip keeps abscission zone healthy When IAA abscission zone becomes sensitive to ethylene

Ethylene Effects Normally IAA from leaf tip keeps abscission zone healthy When IAA abscission zone becomes sensitive to ethylene Ethylene induces hydrolases & leaf falls off

Ethylene Synthesis Made in response to stress, IAA, or during ripening

Ethylene Synthesis Made in response to stress, IAA, or during ripening Use ACC or ethephon (which plants convert to ethylene) to synchronize flowering, speed ripening

Ethylene Synthesis Made in response to stress, IAA, or during ripening Use ACC or ethephon (which plants convert to ethylene) to synchronize flowering, speed ripening Recent work shows ACC has own effects

Ethylene Synthesis Made in response to stress, IAA, or during ripening Use ACC or ethephon (which plants convert to ethylene) to synchronize flowering, speed ripening Recent work shows ACC has own effects Use silver & other inhibitors to preserve flowers & fruit

Ethylene Signaling Receptors were identified by mutants in triple response

Ethylene Signaling Receptors were identified by mutants in triple response Also resemble bacterial 2-component signaling systems!

Ethylene Signaling Receptors were identified by mutants in triple response Also resemble bacterial 2-component signaling systems! Receptor is in ER!

Ethylene Signaling 1. In absence of ethylene, receptors activate CTR1 which represses EIN2-dependent signaling

Ethylene Signaling In absence of ethylene, receptors activate CTR1 which represses EIN2-dependent signaling Upon binding ethylene, receptors inactivate CTR1 by unknown mech

Ethylene Signaling In absence of ethylene, receptors activate CTR1 which represses EIN2-dependent signaling Upon binding ethylene, receptors inactivate CTR1 by unknown mech 3. Active EIN2 activates EIN3

Ethylene Signaling In absence of ethylene, receptors activate CTR1 which represses EIN2-dependent signaling Upon binding ethylene, receptors inactivate CTR1 by unknown mech 3. Active EIN2 activates EIN3 4. EIN3 turns on genes needed for ethylene response.

Ethylene Signaling In absence of ethylene, receptors activate CTR1 which represses EIN2-dependent signaling Upon binding ethylene, receptors inactivate CTR1 by unknown mech 3. Active EIN2 activates EIN3 4. EIN3 turns on genes needed for ethylene response. 5. Ethylene receptor also turns off EIN3 degradation