1. Help needed for Chester Street Elementary School's STEAM Day
Science stuff with 1st – 5th graders
10-3:30 on Friday March 29
Help needed for dissecting frogs with 7th graders on Friday April 5
8:30- 10:30 in CSC223

2. 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!

3. 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"

4. 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!

5. 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

6. 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

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

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

9. 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

10. 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.

11. 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

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

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

14. 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

15. 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

16. 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

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

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

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

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

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

22. 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

23. 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)!

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

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

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

27. 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

28. Gibberellin signaling
Used mutants to learn about GA signaling

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

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

31. 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

32. 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

33. 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 33

34. 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
D = Asp, E = Glu, L = Leu, A = Ala

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

36. 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)

37. 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

38. 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

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

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

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

42. 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

43. 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

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

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

46. 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

47. 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