Growth regulators Auxins Cytokinins Gibberellins Abscisic Acid Ethylene Brassinoteroids

Growth regulators1.Auxins 2.Cytokinins 3.Gibberellins 4.Abscisic Acid 5.Ethylene 6.Brassinoteroids 7.Jasmonic Acid 8.Salicylic Acid 9.Strigolactones 10.Nitric Oxide 11.Sugars

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)!

GibberellinsGAs 1, 3 & 4 are most bioactiveMade at many locations in plantAct 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

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

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

GA & other hormonesGA 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 hormonesGA 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

ABADiscovered as inhibitor of auxin –induced elongation (inhibitor ).Also found lots in tissues going dormant (dormin)Also found chemicals from senescing leaves & fruits that accelerated

leaf abscission (abscission II)

Was abscisic acid

ABACounteracts GA effects• Causes seed dormancy &

inhibits seed germination• Inhibits fruit ripening

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

ABAMost is made in root & transported to shoot in response to stressCloses stomates by opening Ca then closing K channels

ABASynthesized during seed maturation to promote dormancyAlso closes stomates in stress by opening Ca then closing K channelsInduces many genes (~10% of total) via several different mechs1. bZIP/ABRE (ABI3, 4, 5 + AREBs)

ABASynthesized during seed maturation to promote dormancyAlso closes stomates in stress by opening Ca then closing K channelsInduces many genes (~10% of total) via several different mechs1. bZIP/ABRE (ABI3, 4, 5 + AREBs)2. MYC/MYB

ABAInduces many genes (~10% of total) via several different mechs1. bZIP/ABRE (ABI3, 4, 5 + AREBs)2. 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 signaling3 groups of receptors1. GTG in PM• Resemble GPCR

TAIZ-Zeiger version of ABA signaling3 groups of receptors1. GTG in PM• Resemble GPCR• IP3 has role in ABA• Unclear if GTG causeIP3 production

TAIZ-Zeiger version of ABA signaling3 groups of receptors1. GTG in PM2. CHLH in Cp• Also catalyzes Chl synthesis

TAIZ-Zeiger version of ABA signaling3 groups of receptors1. GTG in PM2. CHLH in Cp• Also catalyzes Chl synthesis• And signals cp damage to nucleus

TAIZ-Zeiger version of ABA signaling3 groups of receptors1. GTG in PM2. CHLH in Cp3. PYR/PYL/RCAR• cytoplasmic

Schroeder version of ABA signaling1. PYR/PYL/RCAR is key player• Binds ABA& inactivates PP2C

Schroeder version of ABA signaling1. PYR/PYL/RCAR is key player• Binds ABA& inactivates PP2C• Allows SnRK2 to function

Schroeder version of ABA signaling1. 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

EthyleneA gas that acts as a hormone!Chinese burned incense to ripen pears1864: leaks from street lamps damage treesNeljubow (1901): ethylene causes triple response: short stems,

swelling & abnormal horizontal growth

EthyleneA gas that acts as a hormone!Chinese burned incense to ripen pears1864: leaks from street lamps damage treesNeljubow (1901): ethylene causes triple response: short stems,

swelling & abnormal horizontal growthDoubt (1917): stimulates abscissionGane (1934): a naturalplant product

Ethylene EffectsClimacteric fruits produce spike of ethylene at start of ripening &

exogenous ethylene enhances this

Ethylene EffectsClimacteric fruits produce spike of ethylene at start of ripening &

exogenous ethylene enhances thisResults: 1) increased respiration2) production of hydrolases & other enzymes involved in ripening

Ethylene EffectsNormally IAA from leaf tip keeps abscission zone healthy

Ethylene EffectsNormally IAA from leaf tip keeps abscission zone healthyWhen IAA abscission zone becomes sensitive to ethylene

Ethylene EffectsNormally IAA from leaf tip keeps abscission zone healthyWhen IAA abscission zone becomes sensitive to ethyleneEthylene induces hydrolases & leaf falls off

Ethylene SynthesisMade in response to stress, IAA, or during ripening

Ethylene SynthesisMade in response to stress, IAA, or during ripeningUse ACC or ethephon (which plants convert to ethylene) to synchronize flowering, speedripening

Ethylene SynthesisMade in response to stress, IAA, or during ripeningUse ACC or ethephon (which plants convert to ethylene) to synchronize flowering, speedripening• Recent workshows ACC has own effects

Ethylene SynthesisMade in response to stress, IAA, or during ripeningUse ACC or ethephon (which plants convert to ethylene) to synchronize flowering, speedripening• Recent workshows ACC has own effects• Use silver & other inhibitors to preserve flowers & fruit

Ethylene SignalingReceptors were identified by mutants in triple response

Ethylene SignalingReceptors were identified by mutants in triple responseAlso resemble bacterial 2-component signaling systems!

Ethylene SignalingReceptors were identified by mutants in triple responseAlso resemble bacterial 2-component signaling systems!Receptor is in ER!

Ethylene Signaling1. In absence of ethylene, receptors activate CTR1 which represses

EIN2-dependent signaling

Ethylene Signaling1. In absence of ethylene, receptors activate CTR1 which represses

EIN2-dependent signaling2. Upon binding ethylene, receptorsinactivate CTR1 by unknown mech

Ethylene Signaling1. In absence of ethylene, receptors activate CTR1 which represses

EIN2-dependent signaling2. Upon binding ethylene, receptorsinactivate CTR1 by unknown mech3. Active EIN2 activates EIN3

Ethylene Signaling1. In absence of ethylene, receptors activate CTR1 which represses

EIN2-dependent signaling2. Upon binding ethylene, receptorsinactivate CTR1 by unknown mech3. Active EIN2 activates EIN34. EIN3 turns on genes needed for ethylene response.

Ethylene Signaling1. In absence of ethylene, receptors activate CTR1 which represses

EIN2-dependent signaling2. Upon binding ethylene, receptorsinactivate CTR1 by unknown mech3. Active EIN2 activates EIN34. EIN3 turns on genes needed for ethylene response.5. Ethylene receptor also turns off EIN3 degradation