1. Growth regulators
Auxins
Cytokinins
Gibberellins
Abscisic Acid
Ethylene
Brassinoteroids
Jasmonic Acid
Salicylic Acid
Strigolactones
Nitric Oxide
Sugars

2. 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)!

3. 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

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

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

6. 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

7. 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

8. 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

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

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

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

12. 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)

13. 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

14. 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

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

16. 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

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

18. 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

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

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

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

22. 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

23. ABA signaling in Guard Cells

24. 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

25. 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

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

27. 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

28. Ethylene Effects
Normally IAA from leaf tip keeps abscission zone healthy

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

30. 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

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

32. 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

33. 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

34. 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

35. Ethylene Signaling
Receptors were identified by mutants in triple response

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

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

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

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

40. 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

41. 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.

42. 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