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

7. Hypersensitive response

8. Systemic acquired immunity

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

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

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 Proc Natl Acad Sci U S A. 2005 Dec 27;102(52):19237-42. No JAConstitutive JA

13. Crunchers vs suckers

14. Pseudomonas syringae alters the immune balance of the plant

18. RR or Rrrr Avr1No diseaseDISEASE avr1Disease The gene-for-gene resistance model Host Genes Microbe Genes

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

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

26. Crunchers vs suckers

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

28. Fungi must break through the surface of the leaf http://www.nysaes.cornell.edu/pp/faculty/hoch/images/black_ rot6.gif

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

31. Structure of the penetration peg

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

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

34. Callose is deposited at infection sites

35. pen mutants WTpen1 From : Monica Stein, Somerville lab, Stanford

36. pen3 plants allow more hyphal growth than other pen mutants WTpen3 From : Monica Stein, Somerville lab, Stanford

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

38. 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.