1. 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!

2. 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!

3. 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"

4. 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

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

6. 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!

7. 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?

8. 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

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

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

11. 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!

12. 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

13. 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

14. 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

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

16. 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

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

18. 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

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

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

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

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

23. 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

24. 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

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

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

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

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

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

30. Cytokinin Effects
Promote lateral bud growth

31. Cytokinin Effects
Promote lateral bud growth
Delay leaf senescence

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

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

34. Cytokinin Action
1.Cytokinin binds receptor's extracellular domain

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

36. 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)

37. 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

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

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

40. 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.

41. 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

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

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

44. 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

45. 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

46. 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

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

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

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

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

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

52. 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

53. 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)!

54. Gibberellins
>136 gibberellins (based on
structure)!
Most plants have >10

55. Gibberellins
>136 gibberellins (based on
structure)!
Most plants have >10
Activity varies dramatically!

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

57. 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

58. Gibberellin signaling
Used mutants to learn about GA signaling

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

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

61. 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

62. 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

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 63

64. 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

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

66. 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)

67. 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

68. 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

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

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

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

72. 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

73. 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

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

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

76. 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

77. 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

78. 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

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

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

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

82. 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)

83. 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

84. 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

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

86. 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

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

88. 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

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

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

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

92. 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

93. ABA signaling in Guard Cells

94. 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

95. 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

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

97. 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

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

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

100. 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

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

102. 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

103. 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

104. 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

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

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

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

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

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

110. 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

111. 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.

112. 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