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PAMP-triggered immunity (PTI)

PAMP-triggered immunity (PTI). Recognition of danger signals Distinguish self or damaged self versus nonself – fundamental to any immune system PAMP or MAMP – pathogen/microbe-associated molecular pattern DAMP – damage-associated molecular pattern

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PAMP-triggered immunity (PTI)

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  1. PAMP-triggered immunity (PTI) • Recognition of danger signals • Distinguish self or damaged self versus nonself – fundamental to any immune system • PAMP or MAMP – pathogen/microbe-associated molecular pattern • DAMP – damage-associated molecular pattern • PRR – Pattern recognition receptors (receptor-like proteins/kinases) • Membrane receptors • Ligand-receptor interaction • Initiate signal transduction cascade • Conserved features across plants, insects, vertebrates • Adapted pathogens use effectors to suppress • PTI often considered weaker than ETI, but is it really?

  2. The zigzag model for plant pathogen interactions Dangl and Jones. 2006. Nature 444:323-329

  3. How to distinguish a PAMP from an effector?? • PAMPS can be widely conserved or narrowly conserved • Invariant or highly constrained sequence • PAMP is essential for microbial fitness and survival • Effector specifically contributes to virulence by targeting host (defense) physiology • Lines are blurry • From the plant immunity point of view, the nature and intrinsic • function of the ligand is not relevant as long as it timely and accurately betrays the potential microbial invader to the plant surveillance system. As a result of continuous coevolution between plant and pathogen, a wealth of plant perception systems for microbe-derived molecules has been shaped that reliably fulfills roles in mediating the establishment of plant immunity Thomma et al. (2011) Plant Cell 23:4-15

  4. Dubery et al. 2012

  5. Structure of bacterial lipopolysaccharide and peptidoglycan Erbs and Newman (2012) Mol. Plant Pathol. 13:95-104

  6. Pattern recognition receptors (PRRs) • First layer of active defense, extracellular membrane receptors • PRRs perceive PAMPs by typical receptor-ligand interactions • Evolutionarily ancient and some widely occurring in plant kingdom • Interfamily transfer of PRRs more successful than R genes • R proteins in contrast are evolutionarily young, with many novel members • Lines are blurry, some interactions classified as Avr-R gene may be re-classified as PAMP-PRR Thomma et al. (2011) Plant Cell 23:4-15

  7. Receptors of bacterial PAMPS Segonzac and Zipfel (2011) Curr. Opin. Microbiol. 14:54-61

  8. LysM domain-containing receptors Antolin-Llovera et al. (2012) Annu. Rev. Phytopathol. 50:451-473

  9. PRRs and DAMP receptors Monaghan and Zipfel (2012) Curr. Opin. Plant Biol. 15:349-357

  10. Receptor complexes Monaghan and Zipfel (2012) Curr. Opin. Plant Biol. 15:349-357

  11. Dubery et a. 2012

  12. Dubery et al. 2012

  13. RPK-mediated recognition of PAMPs and DAMPs Tena et al. (2011) Curr. Opin. Plant Biol. 14:519-529

  14. MAP Kinase modules involved in response to PAMPs and DAMPs Tena et al. (2011) Curr. Opin. Plant Biol. 14:519-529

  15. FLS2 signaling pathway in Arabidopsis Segonzac and Zipfel (2011) Curr. Opin. Microbiol. 14:54-61

  16. Inhibition of flg22 perception by P. syringaepv. tomato Nurnberger and Kemmerling (2009)

  17. Zigzag model incorporating co-evolution between Cladosporiumfulvumand tomato Ecp6 – LysM effector - competes with CEBiP - present in all C.f. isolates - widely occurs in fungi (chitin scavenging important for virulence) - some tomato genotypes develop HR to Ecp6 Thomma et al. (2011) Plant Cell 23:4-15

  18. Comparison of plant and animal perception of conserved microbial signatures Ronald and Beutler (2010) Science

  19. Some outstanding remaining questions Match more PAMPs to their PRRs PRR specificity? do plants activate congruent pathways to different microbes? How does PTI restrict pathogen growth? Links between PTI and cell death? Where does specificity in signaling occur for different microbes? Can PRRs be pyramided to give broad spectrum immunity? What molecular events initiate distinct signaling branches? How is PTI tightly controlled to avoid autoimmune disorders? Molecular interconnection between ETI and PTI How is PTI connected to hormone pathways involved in growth and development?

  20. Dubery et al. 2012

  21. Dubery et al. 2012

  22. PAMP perception Nurnberger and Kemmerling (2009)

  23. FLS2 signaling pathway Antolin-Llovera et al. (2012) Annu. Rev. Phytopathol. 50:451-473

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