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Plant Defense Responses and Interactions with Pathogens, Pests, and Symbionts

This talk explores plant defense mechanisms, including hypersensitive response, systemic acquired resistance, and innate immunity, as well as interactions with pests, pathogens, and symbionts.

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Plant Defense Responses and Interactions with Pathogens, Pests, and Symbionts

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  1. 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 b1-4 • 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 b1-4 • 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 b1-4 • 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

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