Download No Slide Title

Growth regulators
1.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)!
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
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 diffuses 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
1. 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
1. bZIP/ABRE (ABI3, 4, 5 + AREBs)
2. MYC/MYB
ABA
Induces many genes (~10% of total) via several different mechs
1. 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 signaling
3 groups of receptors
1. GTG in PM
• Resemble GPCR
TAIZ-Zeiger version of ABA signaling
3 groups of receptors
1. 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
1. GTG in PM
2. CHLH in Cp
• Also catalyzes Chl synthesis
TAIZ-Zeiger version of ABA signaling
3 groups of receptors
1. GTG in PM
2. CHLH in Cp
• Also catalyzes Chl synthesis
• And signals cp damage
to nucleus
TAIZ-Zeiger version of ABA signaling
3 groups of receptors
1. GTG in PM
2. CHLH in Cp
3. PYR/PYL/RCAR
• cytoplasmic
Schroeder version of ABA signaling
1. PYR/PYL/RCAR is key player
• Binds ABA& inactivates PP2C
Schroeder version of ABA signaling
1. PYR/PYL/RCAR is key player
• Binds ABA& inactivates PP2C
• Allows SnRK2 to function
Schroeder version of ABA signaling
1. 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
Doubt (1917): stimulates abscission
Gane (1934): a natural
plant product
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 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
1. In absence of ethylene, receptors activate CTR1 which represses
EIN2-dependent signaling
2. Upon binding ethylene, receptors
inactivate CTR1 by unknown mech
Ethylene Signaling
1. In absence of ethylene, receptors activate CTR1 which represses
EIN2-dependent signaling
2. Upon binding ethylene, receptors
inactivate CTR1 by unknown mech
3. Active EIN2 activates EIN3
Ethylene Signaling
1. In absence of ethylene, receptors activate CTR1 which represses
EIN2-dependent signaling
2. 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
1. In absence of ethylene, receptors activate CTR1 which represses
EIN2-dependent signaling
2. 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