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

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

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

7. 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

8. 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

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

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

11. 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

12. 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

13. 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

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

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

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

17. 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)

18. 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

19. 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

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

21. 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

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

23. 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

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

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

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

27. 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

28. ABA signaling in Guard Cells

29. 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

30. 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

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

32. 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

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

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

35. 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

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

37. 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

38. 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

39. 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

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

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

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

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

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

45. 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

46. 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.

47. 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