1. Pathogens Agrobacterium tumefaciens Agrobacterium rhizogenes Pseudomonas syringeae Pseudomonas aeruginosa Viroids DNA viruses RNA viruses Fungi oomycetes nematodes Symbionts N-fixers Endomycorrhizae Ectomycorrhizae

2. 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

3. 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

4. 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)

5. 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  1-4 Cross-link with neighbors to form strong, stable fibers

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

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

8. Plant Cell Walls and Growth Cellulose: ordered chains made of glucose linked  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

9. Plant Cell Walls and Growth Cellulose: ordered chains made of glucose linked  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

10. Plant Cell Walls and Growth Cellulose: ordered chains made of glucose linked  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

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

12. 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

13. 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

14. 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

15. 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

16. 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

17. 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

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

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

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

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

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

23. 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

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

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

26. 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

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

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

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

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

31. Plant Cell Walls and Growth Also 4 main multigenic families of structural proteins Amounts vary between cell types & conditions 1.HRGP: hydroxyproline-rich glycoproteins (eg extensin) Proline changed to hydroxyproline in Golgi

32. Plant Cell Wall Proteins 1.HRGP: hydroxyproline-rich glycoproteins (eg extensin) Proline changed to hydroxyproline in Golgi Highly glycosylated: helps bind CH 2 O

33. Plant Cell Wall Proteins 1.HRGP: hydroxyproline-rich glycoproteins (eg extensin) Proline changed to hydroxyproline in Golgi Highly glycosylated: helps bind CH 2 O Common in cambium, phloem

34. Plant Cell Wall Proteins 1.HRGP: hydroxyproline-rich glycoproteins (eg extensin) Proline changed to hydroxyproline in Golgi Highly glycosylated: helps bind CH 2 O Common in cambium, phloem Help lock the wall after growth ceases

35. Plant Cell Wall Proteins 1.HRGP: hydroxyproline-rich glycoproteins (eg extensin) Proline changed to hydroxyproline in Golgi Highly glycosylated: helps bind CH 2 O Common in cambium, phloem Help lock the wall after growth ceases Induced by wounding 2. PRP: proline-rich proteins

36. Plant Cell Wall Proteins 1.HRGP: hydroxyproline-rich glycoproteins (eg extensin) 2.PRP: proline-rich proteins Low glycosylation = little interaction with CH 2 O

37. Plant Cell Wall Proteins 1.HRGP: hydroxyproline-rich glycoproteins (eg extensin) 2.PRP: proline-rich proteins Low glycosylation = little interaction with CH 2 O Common in xylem, fibers, cortex

38. Plant Cell Wall Proteins 1.HRGP: hydroxyproline-rich glycoproteins (eg extensin) 2.PRP: proline-rich proteins Low glycosylation = little interaction with CH 2 O Common in xylem, fibers, cortex May help lock HRGPs together

39. Plant Cell Wall Proteins 1.HRGP: hydroxyproline-rich glycoproteins (eg extensin) 2.PRP: proline-rich proteins Low glycosylation = little interaction with CH 2 O Common in xylem, fibers, cortex May help lock HRGPs together 3.GRP: Glycine-rich proteins No glycosylation = little interaction with CH 2 O

40. Plant Cell Wall Proteins 1.HRGP: hydroxyproline-rich glycoproteins (eg extensin) 2.PRP: proline-rich proteins Low glycosylation = little interaction with CH 2 O Common in xylem, fibers, cortex May help lock HRGPs together 3.GRP: Glycine-rich proteins No glycosylation = little interaction with CH 2 O Common in xylem

41. Plant Cell Wall Proteins 1.HRGP: hydroxyproline-rich glycoproteins (eg extensin) 2.PRP: proline-rich proteins Low glycosylation = little interaction with CH 2 O Common in xylem, fibers, cortex May help lock HRGPs together 3.GRP: Glycine-rich proteins No glycosylation = little interaction with CH 2 O Common in xylem May help lock HRGPs & PRPs together

42. Plant Cell Wall Proteins 1.HRGP: hydroxyproline-rich glycoproteins (eg extensin) 2.PRP: proline-rich proteins 3. GRP: Glycine-rich proteins No glycosylation = little interaction with CH 2 O Common in xylem May help lock HRGPs & PRPs together 4. Arabinogalactan proteins

43. Plant Cell Wall Proteins 1.HRGP: hydroxyproline-rich glycoproteins (eg extensin) 2.PRP: proline-rich proteins 3. GRP: Glycine-rich proteins 4. Arabinogalactan proteins Highly glycosylated: helps bind CH 2 O

44. Plant Cell Wall Proteins 1.HRGP: hydroxyproline-rich glycoproteins (eg extensin) 2.PRP: proline-rich proteins 3. GRP: Glycine-rich proteins 4. Arabinogalactan proteins Highly glycosylated: helps bind CH 2 O Anchored to PM by GPI

45. Plant Cell Wall Proteins 1.HRGP: hydroxyproline-rich glycoproteins (eg extensin) 2.PRP: proline-rich proteins 3. GRP: Glycine-rich proteins 4. Arabinogalactan proteins Highly glycosylated: helps bind CH 2 O Anchored to PM by GPI Help cell adhesion and cell signaling

46. Plant Cell Wall Proteins 1.HRGP: hydroxyproline-rich glycoproteins (eg extensin) 2.PRP: proline-rich proteins 3. GRP: Glycine-rich proteins 4. Arabinogalactan proteins Highly glycosylated: helps bind CH 2 O Anchored to PM by GPI Help cell adhesion and cell signaling 5. Also many enzymes involved in cell wall synthesis and loosening

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

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

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

50. Plant Cell Walls and Growth Lignins = polyphenolic macromolecules: 2 nd 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

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

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

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

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

55. 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

56. 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

57. 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

58. 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

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

60. 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

61. 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

62. 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

63. 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

64. 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!

65. 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

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

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

68. 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

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

70. 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

71. 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

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

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

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

75. 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

76. Growth regulators 1.Auxins 2.Cytokinins 3.Gibberellins 4.Abscisic acid 5.Ethylene 6.Brassinosteroids All are small organics: made in one part, affect another part

77. 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!

78. Auxin First studied by Darwins! Showed that a "transmissible influence" made at tips caused bending lower down

79. Auxin First studied by Darwins! Showed that a "transmissible influence" made at tips caused bending lower down No tip, no curve!

80. Auxin First studied by Darwins! Showed that a "transmissible influence" made at tips caused bending lower down No tip, no curve! 1913:Boysen-Jensen showed that diffused through agar blocks but not through mica

81. Auxin 1913:Boysen-Jensen showed that diffused through agar blocks but not through mica 1919: Paal showed that if tip was replaced asymmetrically, plant grew asymmetrically even in dark

82. Auxin 1913:Boysen-Jensen showed that diffused through agar blocks but not through mica 1919: Paal showed that if tip was replaced asymmetrically, plant grew asymmetrically even in dark Uneven amounts of "transmissible influence" makes bend

83. Auxin 1919: Paal showed that if tip was replaced asymmetrically, plant grew asymmetrically even in dark Uneven amounts of "transmissible influence" makes bend 1926: Went showed that a chemical that diffused from tips into blocks caused growth

84. Auxin 1919: Paal showed that if tip was replaced asymmetrically, plant grew asymmetrically even in dark Uneven amounts of "transmissible influence" makes bend 1926: Went showed that a chemical that diffused from tips into blocks caused growth If placed asymmetrically get bending due to asymmetrical growth

85. Auxin 1919: Paal showed that if tip was replaced asymmetrically, plant grew asymmetrically even in dark Uneven amounts of "transmissible influence" makes bend 1926: Went showed that a chemical that diffused from tips into blocks caused growth If placed asymmetrically get bending due to asymmetrical growth Amount of bending depends on [auxin]

86. Auxin 1919: Paal showed that if tip was replaced asymmetrically, plant grew asymmetrically even in dark Uneven amounts of "transmissible influence" makes bend 1926: Went showed that a chemical that diffused from tips into blocks caused growth If placed asymmetrically get bending due to asymmetrical growth Amount of bending depends on [auxin] 1934: Indole-3-Acetic acid (IAA) from the urine of pregnant women was shown to cause bending

87. Auxin 1934: Indole-3-Acetic acid (IAA) from the urine of pregnant women was shown to cause bending IAA is the main auxin in vivo. Others include Indole-3-butyric acid (IBA), 4-Chloroindole-3-acetic acid and phenylacetic acid (PA)IBA PA 4-CI-IAA IAA

88. Auxin IAA is the main auxin in vivo. Many synthetic auxins have been identifiedIAA

89. Auxin IAA is the main auxin in vivo. Many synthetic auxins have been identified No obvious structural similarity, yet all work!IAA

90. Auxin IAA is the main auxin in vivo. Many synthetic auxins have been identified No obvious structural similarity, yet all work! Widely used in agricultureIAA

91. Auxin IAA is the main auxin in vivo. Many synthetic auxins have been identified No obvious structural similarity, yet all work! Widely used in agriculture to promote growth (flowering, cuttings)IAA

92. Auxin IAA is the main auxin in vivo. Many synthetic auxins have been identified No obvious structural similarity, yet all work! Widely used in agriculture to promote growth (flowering, cuttings) as weed killers! Agent orange was 1:1 2,4-D and 2,4,5-TIAA