Prepare a 10

1
Prepare a 10talk for Friday Feb 27 on plant
defense responses or describe interactions
between plants pathogens or symbionts

• Plant defense responses
• Hypersensitive response
• Systemic acquired resistance
• Innate immunity
• Phytoalexin synthesis
• Defensins and other proteins
• Oxidative burst

• Some possible pathogens
• Agrobacterium tumefaciens
• Agrobacterium rhizogenes
• Pseudomonas syringeae
• Pseudomonas aeruginosa
• Viroids
• DNA viruses
• RNA viruses
• Fungi
• Oomycetes
• Some possible symbionts
• N-fixing bacteria
• N-fixing cyanobacteria
• Endomycorrhizae
• Ectomycorrhizae

2

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

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" Some
early genes turn on 'late genes" needed for
development
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 Discovered as factors which induce
cultured cells to divide Haberlandt (1913)
phloem chemical stimulates division
7
Cytokinins Discovered as factors which induce
cultured cells to divide Haberlandt (1913)
phloem chemical stimulates division van Overbeek
(1941) coconut milk stimulates division
8
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!
9
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
10
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
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! Kinetin was the breakdown
product Derived from adenine Requires auxin to
stimulate division
12
Cytokinins Requires auxin to stimulate
division Kinetin/auxin determines tissue formed
(original fig)
13
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
14
Cytokinins Miller Letham (1961) simultaneously
found zeatin Later found in many spp including
coconut milk Kinetin
trans-Zeatin
15
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
16
Cytokinins Many other natural synthetics have
been identified Like auxins, many are bound to
sugars or nucleotides
17
Cytokinins Many other natural synthetics have
been identified Like auxins, many are bound to
sugars or nucleotides Inactive, but easily
converted
18

• Cytokinin Synthesis
• Most cytokinins are made at root
• apical meristem transported to
• sinks in xylem

19

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

20

• 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

21

• 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

22

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

23

• Cytokinin Effects
• Regulate cell division
• Need mutants defective in CK metabolism or
  signaling to detect this in vivo
• SAM plants are smaller when
• CK

24

• Cytokinin Effects
• SAM plants are smaller when CK
• Roots are longer!

25

• Cytokinin Effects
• Usually roots have too much CK inhibits
  division!
• Cytokinins mainly act _at_ root shoot meristems

26

• Cytokinin Effects
• Cytokinins mainly act _at_ root shoot meristems
• Control G1-gt S G2-gt M transition

27

• Cytokinin Effects
• Promote lateral bud growth

28

• Cytokinin Effects
• Promote lateral bud growth
• Delay leaf senescence

29

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

30

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

31

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

32

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

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• 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)

34

• 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

35

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

36

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

37

• 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.

38

• 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

39

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

40

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

41

• 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

42

• 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

43

• 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

44

• Gibberellins
• Discovered in plants in 1950s
• "rescued" some dwarf corn pea mutants

45

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

46

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

47

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

48

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

49

• 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

50

• 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
• gt136 gibberellins (based on
• structure)!

51

• Gibberellins
• gt136 gibberellins (based on
• structure)!
• Most plants have gt10

52

• Gibberellins
• gt136 gibberellins (based on
• structure)!
• Most plants have gt10
• Activity varies dramatically!

53

• Gibberellins
• gt136 gibberellins (based on
• structure)!
• Most plants have gt10
• Activity varies dramatically!
• Most are precursors or
• degradation products

54

• Gibberellins
• gt136 gibberellins (based on
• structure)!
• Most plants have gt10
• Activity varies dramatically!
• Most are precursors or
• degradation products
• GAs 1, 3 4 are most bioactive

55
Gibberellin signaling Used mutants to learn about
GA signaling
56

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

57

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

58

• 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

59

• 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

60

• 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

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
• encode GA receptors
• Sly E3 receptors
• DELLA (eg rga)
• repressors of GA signaling

62
Gibberellins GAs 1, 3 4 are most bioactive Act
by triggering degradation of DELLA repressors
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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)
64
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
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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