plant immune system presentation.pptx (read-only) · introducbon$ $$ • pathogens( bacteria,...
TRANSCRIPT
IntroducBon
• Pathogens (bacteria, nematodes, aphids, fungi,...) have different life strategies.
• Usage of effectors to enhance microbial fitness
• Plants rely on innate immunity of each cell
• 2-‐layered plant immune system: – PRRs outside the cell – NB-‐LRRs inside the cell à R-‐Proteins
Flagellin and other MAMPs • Flagellin is important for pathogenicity in plants
• flg22 induces many cellular responses
• FLS2 binds flg22 – acts against early pathogen invasion
• Others: – Bacterial cold shock proteins – ElongaBon factor Tu EF-‐Tu – recognized by EFR
MAMP/PAMP Response
• Limited MAMP/PAMP responsiveness within plant species – Individual species recognize a subset of PAMPs
• Over 200 LRR-‐kinases in Arabidopsis genome
Effectors
• Structural roles – extrahaustorial matrix
• Promote nutrient leakage • Pathogen dispersal • Mimic or inhibit eucaryoBc cell funcBons • Bacteria deliver 15-‐30/strain into the host cell via Type III secreBon system TTSS
• Contribute to PTI/ETI suppression
Fungal and oomycete effectors
• Act either in the extracellular matrix or in the host
• Are recognized by RLPs or NB-‐LRRs • Huge effector-‐diversity • How fungal and oomycete effectors are delivered into the cell and how they contribute to virulence is unknown!
Pathogens and Plant Hormones
• Pathogen effectors mimic plant hormones
Pseudomonas syringae: corona9ne
Ø Suppresses defence to biotrophs Ø Opens stomata – access for bacteria
Host RecogniBon of Pathogen Effectors
• Effectors overcoming PTI are recognized by NB-‐LRR à ETI • Recognized effector = avirulence protein Avr • ETI is faster and stronger than PTI – o`en leads to HR
Guard Hypothesis
1. An effector has a target(s) in the host 2. ManipulaBng/altering this target
contributes to pathogen success in suscepBble hosts
3. A “pathogen induced modified self“ acBvates the corresponding NB-‐LRR, leading to ETI
Signalling
• NB-‐LRR folded in a signal competent state • LRRs block inappropriate NB acBvaBon • Cross-‐talk to differenBate biotrophs from necrotrophs – Biotrophs: salicylic acid – Necrotrophs: jasmonic acid & ethylene
• AddiBonal plant hormones involved
Challenges and OpportuniBes
• Define effector-‐repertoire and modes of acBon
• Understanding of PTI and ETI and what causes pathogen growth arrest?
• Understanding the populaBon biology of effectors and NB-‐LRR-‐genes
Innate Immunity in Plants: An Arms Race Between Paeern RecogniBon Receptors in Plants and Effectors in
Microbial Pathogens Thomas Boller and Sheng Yang He
Science 2009
Lea Stauber
PTI – the First Defence Layer
• High specificity and sensiBvity of PRRs
• MAMP is recognized through conserved epitope (e.g. flg22)
• PRR focuses on highly conserved MAMP-‐domain
Suppression of PTI (2)
• Bacterial virulence factors supress PTI
• Effectors AvrPto and AvrPtoB physically interact with PRR-‐kinases (e.g. FLS2, EFR)
• Physical interacBon inhibits PRRs
• AvrPtoB –domain degrades PRRs and may defeat PTI