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Types of plant pathogens

Types of plant pathogens. Necrotrophic pathogen. Biotrophic pathogen. Hemibiotrophic. Plants cannot do many things. Plants have disposable body parts; we don’t. Basic defenses of a plant. Living in the apoplast. Hypersensitive responses kill small parts of the leaf.

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Types of plant pathogens

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  1. Types of plant pathogens Necrotrophic pathogen Biotrophic pathogen Hemibiotrophic

  2. Plants cannot do many things

  3. Plants have disposable body parts; we don’t

  4. Basic defenses of a plant

  5. Living in the apoplast

  6. Hypersensitive responses kill small parts of the leaf res2.agr.gc.ca/ecorc/ corn-mais/images/fig-22.jpg http://ppathw3.cals.cornell.edu/PhotoLab/Stills/Tobacco/Tobacco.jpg

  7. Hypersensitive response

  8. Systemic acquired immunity

  9. Involves salicylate but this is not the factor acting through the plant No Salicylate wt No SAR in scion Vernooij, B. et al. 1994, Plant Cell 6: 959-965

  10. TMV plaques in scion leaves X/N N/X N/N X/X Vernooij, B. et al. 1994, Plant Cell 6: 959-965

  11. JA induction by insects and necrotrophs Biochemistry and Molecular Biology of Plants, Buchanan et al. ed, 2000

  12. Arginine and threonine depletion in the gut No JA Constitutive JA Proc Natl Acad Sci U S A. 2005 Dec 27;102(52):19237-42.

  13. Crunchers vs suckers

  14. Pseudomonas syringae alters the immune balance of the plant

  15. The gene-for-gene resistance model Host Genes Microbe Genes

  16. Similarity between R genes and Toll Staskawicz B.J. et al. Science, 2001 5525: 2285-9

  17. Bacteria secrete proteins into the plant cell Cytoplasm using a type III secretion system Host cytoplasm Bacterial cell

  18. Crunchers vs suckers

  19. Mi-1 is an R gene giving resistance to nematode and aphid infection Wild type: Aphid infested Carrying Mi-1 Vos, P. et al. 1998 Nature Biotechnology 16: 1365-69

  20. http://www.nysaes.cornell.edu/pp/faculty/hoch/images/black_rot6.gifhttp://www.nysaes.cornell.edu/pp/faculty/hoch/images/black_rot6.gif Fungi must break through the surface of the leaf

  21. Arabidopsis powdery mildew Erysiphe cichoracearum Barley powdery mildew (Bgh) Blumeria graminis f.sp hordei Host infection on Barley Host infection on Arabidopsis Nonhost infection on Arabidopsis From : Monica Stein, Somerville lab, Stanford

  22. Structure of the penetration peg

  23. Erysiphe cichoracearum on Arabidopsis Blumeria graminis f.sp. hordei on Arabidopsis Appressorium Spore Spore A) germination and attempted penetration Appressorium Nonhost: 90% Host: 95% Hypha B) penetration and haustorial development haustorium haustorium Host: 90% Nonhost: 4% hyphae C) Hyphal elongation hyphae Nonhost: 2% Host: 90% cell death D) Conidiation Host: 90% Nonhost: 0% conidia

  24. Cytological Characterization (Zimmerli,L; Stein,M; Lipka,V; Schulze-Lefert,P; Somerville,SC, Plant Journal (2004)) host • callose deposition in response to pathogen attack was dramatically different between host and nonhost inoculation. Papillae H P • Nonhost haustoria were rapidly encased in callose nonhost From : Monica Stein, Somerville lab, Stanford

  25. Callose is deposited at infection sites

  26. pen mutants WT pen1 From : Monica Stein, Somerville lab, Stanford

  27. pen3 plants allow more hyphal growth than other pen mutants WT pen3 From : Monica Stein, Somerville lab, Stanford

  28. * * * P<.0001 P<.01 Phenotype Quantification ** ** ** % of germinated spores pen1 pen2 pen3 ** * * Penetration Elongated Hyphae From : Monica Stein, Somerville lab, Stanford

  29. The story is complicated: Mutation of the callose synthase increases resistance to a fungal pathogen Nishimura, M.T. et al. Science 2003 301: 969-72.

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