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Plant defense responses Hypersensitive response

Published byἈράχνη Αλεξανδρίδης Modified over 6 years ago

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Presentation on theme: "Plant defense responses Hypersensitive response"— Presentation transcript:

1 Plant defense responses Hypersensitive response
Prepare a 10’ talk for Friday March 3 on plant defense responses or describe interactions between plants& pathogens, pests or symbionts Plant defense responses Hypersensitive response Systemic acquired resistance Innate immunity Phytoalexin synthesis Defensins and other proteins Oxidative burst Some possible pests Nematodes Rootworms Aphids Thrips Gypsy moths hemlock woolly adelgid 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 Plant Growth Size & shape depends on cell # & cell size Decide when,where and which way to divide

3 Plant Growth Size & shape depends on cell # & cell size Decide which way to divide & which way to elongate Periclinal = perpendicular to surface

4 Plant Growth Size & shape depends on cell # & cell size Decide which way to divide & which way to elongate Periclinal = perpendicular to surface: get longer

5 Plant Growth Size & shape depends on cell # & cell size Decide which way to divide & which way to elongate Periclinal = perpendicular to surface: get longer Anticlinal = parallel to surface

6 Plant Growth Size & shape depends on cell # & cell size Decide which way to divide & which way to elongate Periclinal = perpendicular to surface: get longer Anticlinal = parallel to surface: add more layers

7 Plant Growth Decide which way to divide & which way to elongate Periclinal = perpendicular to surface: get longer Anticlinal = parallel to surface: add more layers Now must decide which way to elongate

8 Plant Growth Decide which way to divide & which way to elongate Periclinal = perpendicular to surface: get longer Anticlinal = parallel to surface: add more layers Now must decide which way to elongate: which walls to stretch

9 Plant Cell Walls and Growth
Carbohydrate barrier surrounding cell Protects & gives cell shape

10 Plant Cell Walls and Growth
Carbohydrate barrier surrounding cell Protects & gives cell shape 1˚ wall made first mainly cellulose Can stretch!

11 Plant Cell Walls and Growth
Carbohydrate barrier surrounding cell Protects & gives cell shape 1˚ wall made first mainly cellulose Can stretch! 2˚ wall made after growth stops Lignins make it tough

12 Plant Cell Walls and Growth
1˚ wall made first mainly cellulose Can stretch! Control elongation by controlling orientation of cell wall fibers as wall is made

13 Plant Cell Walls and Growth
1˚ wall made first mainly cellulose Can stretch! Control elongation by controlling orientation of cell wall fibers as wall is made 1˚ walls = 25% cellulose, 25% hemicellulose, 35% pectin, 5% protein (but highly variable)

14 Plant Cell Walls and Growth
1˚ walls = 25% cellulose, 25% hemicellulose, 35% pectin, 5% protein (but highly variable) Cellulose: ordered chains made of glucose linked b 1-4

15 Plant Cell Walls and Growth
1˚ walls = 25% cellulose, 25% hemicellulose, 35% pectin, 5% protein (but highly variable) Cellulose: ordered chains made of glucose linked b 1-4 Cross-link with neighbors to form strong, stable fibers

16 Plant Cell Walls and Growth
Cellulose: ordered chains made of glucose linked b 1-4 Cross-link with neighbors to form strong, stable fibers Made by enzyme embedded in the plasma membrane

17 Plant Cell Walls and Growth
Cellulose: ordered chains made of glucose linked b 1-4 Cross-link with neighbors to form strong, stable fibers Made by enzyme embedded in the plasma membrane Guided by cytoskeleton

18 Plant Cell Walls and Growth
Cellulose: ordered chains made of glucose linked b 1-4 Cross-link with neighbors to form strong, stable fibers Made by enzyme embedded in the plasma membrane Guided by cytoskeleton Cells with poisoned µtubules are misshapen

19 Plant Cell Walls and Growth
Cellulose: ordered chains made of glucose linked b 1-4 Cross-link with neighbors to form strong, stable fibers Made by enzyme embedded in the plasma membrane Guided by cytoskeleton Cells with poisoned µtubules are misshapen Other wall chemicals are made in Golgi & secreted

20 Plant Cell Walls and Growth
Cellulose: ordered chains made of glucose linked b 1-4 Cross-link with neighbors to form strong, stable fibers Made by enzyme embedded in the plasma membrane Guided by cytoskeleton Cells with poisoned µtubules are misshapen Other wall chemicals are made in Golgi & secreted Only cellulose pattern is tightly controlled

21 Plant Cell Walls and Growth
Cellulose pattern is tightly controlled 6 CES enzymes form a “rosette”: each makes 6 chains -> 36/fiber

22 Plant Cell Walls and Growth
Cellulose pattern is tightly controlled 6 CES enzymes form a “rosette”: each makes 6 chains -> 36/fiber Rosettes are guided by microtubules

23 Plant Cell Walls and Growth
Cellulose pattern is tightly controlled 6 CES enzymes form a “rosette”: each makes 6 chains Rosettes are guided by microtubules Deposition pattern determines direction of elongation

24 Plant Cell Walls and Growth
Cellulose pattern is tightly controlled Deposition pattern determines direction of elongation New fibers are perpendicular to growth direction, yet fibers form a mesh

25 Plant Cell Walls and Growth
New fibers are perpendicular to growth direction, yet fibers form a mesh Multinet hypothesis: fibers reorient as cell elongates Old fibers are anchored so gradually shift as cell grows

26 Plant Cell Walls and Growth
New fibers are perpendicular to growth direction, yet fibers form a mesh Multinet hypothesis: fibers reorient as cell elongates Old fibers are anchored so gradually shift as cell grows Result = mesh

27 Plant Cell Walls and Growth
1˚ walls = 25% cellulose, 25% hemicellulose, 35% pectin, 5% protein (but highly variable) Hemicelluloses AKA cross-linking glycans: bind cellulose

28 Plant Cell Walls and Growth
Hemicelluloses AKA cross-linking glycans: bind cellulose Coat cellulose & bind neighbor

29 Plant Cell Walls and Growth
Hemicelluloses AKA cross-linking glycans Coat cellulose & bind neighbor Diverse group of glucans: also linked b 1-4, but may have other sugars and components attached to C6

30 Hemicelluloses Diverse group of glucans: also linked b 1-4, but may have other sugars and components attached to C6 makes digestion more difficult

31 Hemicelluloses Diverse group of glucans: also linked b 1-4, but may have other sugars and components attached to C6 makes digestion more difficult Assembled in Golgi

32 Plant Cell Walls and Growth
Hemicelluloses AKA cross-linking glycans A diverse group of glucans also linked b 1-4, but may have other sugars and components attached to C6 makes digestion more difficult Assembled in Golgi Secreted cf woven

33 Plant Cell Walls and Growth
1˚ walls = 25% cellulose, 25% hemicellulose, 35% pectin, 5% protein (but highly variable) Pectins: fill space between cellulose-hemicellulose fibers

34 Pectins Pectins: fill space between cellulose-hemicellulose fibers Form gel that determines cell wall porosity(& makes jam)

35 Pectins Pectins: fill space between cellulose-hemicellulose fibers Form gel that determines cell wall porosity (& makes jam) Acidic, so also modulate pH & bind polars

36 Pectins Pectins: fill space between cellulose-hemicellulose fibers Form gel that determines cell wall porosity (& makes jam) Acidic, so also modulate pH & bind polars Backbone is 1-4 linked galacturonic acid

37 Pectins Backbone is 1-4 linked galacturonic acid Have complex sugar side-chains, vary by spp.

38 Pectins Backbone is 1-4 linked galacturonic acid Have complex sugar side-chains, vary by spp.

39 Plant Cell Walls and Growth
Also 4 main multigenic families of structural proteins

40 Plant Cell Walls and Growth
Also 4 main multigenic families of structural proteins Amounts vary between cell types & conditions

41 Plant Cell Walls and Growth
Also 4 main multigenic families of structural proteins Amounts vary between cell types & conditions HRGP: hydroxyproline-rich glycoproteins (eg extensin) Proline changed to hydroxyproline in Golgi

42 Plant Cell Wall Proteins
HRGP: hydroxyproline-rich glycoproteins (eg extensin) Proline changed to hydroxyproline in Golgi Highly glycosylated: helps bind CH2O

43 Plant Cell Wall Proteins
HRGP: hydroxyproline-rich glycoproteins (eg extensin) Proline changed to hydroxyproline in Golgi Highly glycosylated: helps bind CH2O Common in cambium, phloem

44 Plant Cell Wall Proteins
HRGP: hydroxyproline-rich glycoproteins (eg extensin) Proline changed to hydroxyproline in Golgi Highly glycosylated: helps bind CH2O Common in cambium, phloem Help lock the wall after growth ceases

45 Plant Cell Wall Proteins
HRGP: hydroxyproline-rich glycoproteins (eg extensin) Proline changed to hydroxyproline in Golgi Highly glycosylated: helps bind CH2O Common in cambium, phloem Help lock the wall after growth ceases Induced by wounding 2. PRP: proline-rich proteins

46 Plant Cell Wall Proteins
HRGP: hydroxyproline-rich glycoproteins (eg extensin) PRP: proline-rich proteins Low glycosylation = little interaction with CH2O

47 Plant Cell Wall Proteins
HRGP: hydroxyproline-rich glycoproteins (eg extensin) PRP: proline-rich proteins Low glycosylation = little interaction with CH2O Common in xylem, fibers, cortex

48 Plant Cell Wall Proteins
HRGP: hydroxyproline-rich glycoproteins (eg extensin) PRP: proline-rich proteins Low glycosylation = little interaction with CH2O Common in xylem, fibers, cortex May help lock HRGPs together

49 Plant Cell Wall Proteins
HRGP: hydroxyproline-rich glycoproteins (eg extensin) PRP: proline-rich proteins Low glycosylation = little interaction with CH2O Common in xylem, fibers, cortex May help lock HRGPs together GRP: Glycine-rich proteins No glycosylation = little interaction with CH2O

50 Plant Cell Wall Proteins
HRGP: hydroxyproline-rich glycoproteins (eg extensin) PRP: proline-rich proteins Low glycosylation = little interaction with CH2O Common in xylem, fibers, cortex May help lock HRGPs together GRP: Glycine-rich proteins No glycosylation = little interaction with CH2O Common in xylem

51 Plant Cell Wall Proteins
HRGP: hydroxyproline-rich glycoproteins (eg extensin) PRP: proline-rich proteins Low glycosylation = little interaction with CH2O Common in xylem, fibers, cortex May help lock HRGPs together GRP: Glycine-rich proteins No glycosylation = little interaction with CH2O Common in xylem May help lock HRGPs & PRPs together

52 Plant Cell Wall Proteins
HRGP: hydroxyproline-rich glycoproteins (eg extensin) PRP: proline-rich proteins 3. GRP: Glycine-rich proteins No glycosylation = little interaction with CH2O Common in xylem May help lock HRGPs & PRPs together 4. Arabinogalactan proteins

53 Plant Cell Wall Proteins
HRGP: hydroxyproline-rich glycoproteins (eg extensin) PRP: proline-rich proteins 3. GRP: Glycine-rich proteins 4. Arabinogalactan proteins Highly glycosylated: helps bind CH2O

54 Plant Cell Wall Proteins
HRGP: hydroxyproline-rich glycoproteins (eg extensin) PRP: proline-rich proteins 3. GRP: Glycine-rich proteins 4. Arabinogalactan proteins Highly glycosylated: helps bind CH2O Anchored to PM by GPI

55 Plant Cell Wall Proteins
HRGP: hydroxyproline-rich glycoproteins (eg extensin) PRP: proline-rich proteins 3. GRP: Glycine-rich proteins 4. Arabinogalactan proteins Highly glycosylated: helps bind CH2O Anchored to PM by GPI Help cell adhesion and cell signaling

56 Plant Cell Wall Proteins
HRGP: hydroxyproline-rich glycoproteins (eg extensin) PRP: proline-rich proteins 3. GRP: Glycine-rich proteins 4. Arabinogalactan proteins Highly glycosylated: helps bind CH2O Anchored to PM by GPI Help cell adhesion and cell signaling 5. Also many enzymes involved in cell wall synthesis and loosening

57 Plant Cell Walls and Growth
Also many enzymes involved in cell wall synthesis and loosening As growth stops, start making lignins & linking HGRP

58 Plant Cell Walls and Growth
As growth stops, start depositing lignins & linking HGRP Lignins = polyphenolic macromolecules: 2nd most abundant on earth (after cellulose)

59 Plant Cell Walls and Growth
Lignins = polyphenolic macromolecules: 2nd most abundant on earth (after cellulose) Bond hemicellulose: solidify & protect cell wall (nature’s cement): very difficult to digest

60 Plant Cell Walls and Growth
Lignins = polyphenolic macromolecules: 2nd most abundant on earth (after cellulose) Bond hemicellulose: solidify & protect cell wall (nature’s cement): very difficult to digest Monomers are made in cytoplasm & secreted

61 Plant Cell Walls and Growth
Monomers are made in cytoplasm & secreted Peroxidase & laccase in cell wall create radicals that polymerise non-enzymatically

62 Plant Cell Walls and Growth
Monomers are made in cytoplasm & secreted Peroxidase & laccase in cell wall create radicals that polymerise non-enzymatically

63 Plant Cell Walls and Growth
Peroxidase & laccase in cell wall create radicals that polymerise non-enzymatically Very difficult to digest, yet major plant component!

64 Plant Cell Walls and Growth
As growth stops, start depositing lignins & linking HGRP Solidify & protect cell wall: very difficult to digest Elongation precedes lignification

65 Plant Cell Walls and Growth
As growth stops, start depositing lignins & linking HGRP Solidify & protect cell wall: very difficult to digest Elongation precedes lignification Requires loosening the bonds joining the cell wall

66 Plant Cell Walls and Growth
Elongation precedes lignification Requires loosening the bonds joining the cell wall Can’t loosen too much or cell will burst

67 Plant Cell Walls and Growth
Elongation precedes lignification Requires loosening the bonds joining the cell wall Can’t loosen too much or cell will burst Must coordinate with cell wall synthesis so wall stays same

68 Plant Cell Walls and Growth
Elongation: loosening the bonds joining the cell wall Can’t loosen too much or cell will burst Must coordinate with cell wall synthesis so wall stays same Must weaken crosslinks joining cellulose fibers

69 Plant Cell Walls and Growth
Must weaken crosslinks joining cellulose fibers Turgor pressure then makes cells expand

70 Plant Cell Walls and Growth
Must weaken crosslinks joining cellulose fibers Turgor pressure then makes cells expand Lower pH: many studies show that lower pH is sufficient for cell elongation

71 Plant Cell Walls and Growth
Must weaken crosslinks joining cellulose fibers Lower pH: many studies show that lower pH is sufficient for cell elongation Acid growth hypothesis: Growth regulators cause elongation by activating H+ pump

72 Plant Cell Walls and Growth
Acid growth hypothesis: Growth regulators cause elongation by activating H+ pump Inhibitors of H+ pump stop elongation But: Cosgrove isolated proteins that loosen cell wall Test protein extracts to see if wall loosens

73 Plant Cell Walls and Growth
Acid growth hypothesis: Growth regulators cause elongation by activating H+ pump But: Cosgrove isolated proteins that loosen cell wall Test protein extracts to see if wall loosens Identified expansin proteins that enhance acid growth

74 Plant Cell Walls and Growth
Acid growth hypothesis: Growth regulators cause elongation by activating H+ pump But: Cosgrove isolated proteins that loosen cell wall Test protein extracts to see if wall loosens Identified expansin proteins that enhance acid growth Still don’t know how they work!

75 Plant Cell Walls and Growth
Identified expansin proteins that enhance acid growth Still don’t know how they work! Best bet, loosen Hemicellulose/cellulose bonds

76 Plant Cell Walls and Growth
Also have endoglucanases and transglucanases that cut & reorganize hemicellulose & pectin

77 Plant Cell Walls and Growth
Also have endoglucanases and transglucanases that cut & reorganize hemicellulose & pectin XET (xyloglucan endotransglucosylase) is best-known

78 Plant Cell Walls and Growth
Also have endoglucanases and transglucanases that cut & reorganize hemicellulose & pectin XET (xyloglucan endotransglucosylase) is best-known Cuts & rejoins hemicellulose in new ways

79 Plant Cell Walls and Growth
XET is best-known Cuts & rejoins hemicellulose in new ways Expansins & XET catalyse cell wall creepage

80 Plant Cell Walls and Growth
XET is best-known Cuts & rejoins hemicellulose in new ways Expansins & XET catalyse cell wall creepage Updated acid growth hypothesis: main function of lowering pH is activating expansins and glucanases

81 Plant Cell Walls and Growth
Updated acid growth hypothesis: main function of lowering pH is activating expansins and glucanases Coordinated with synthesis of new cell wall to keep thickness constant

82 Plant Cell Walls and Signaling
Pathogens must digest cell wall to enter plant

83 Plant Cell Walls and Signaling
Pathogens must digest cell wall to enter plant Release cell wall fragments

84 Plant Cell Walls and Signaling
Pathogens must digest cell wall to enter plant Release cell wall fragments Many oligosaccharides signal”HELP!”

85 Plant Cell Walls and Signaling
Pathogens must digest cell wall to enter plant Release cell wall fragments Many oligosaccharides signal”HELP!” Elicit plant defense responses

86 Growth regulators Auxins Cytokinins Gibberellins Abscisic acid Ethylene Brassinosteroids All are small organics: made in one part, affect another part

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