Plant response to bacterial TypeIII effectors

Lihua 12.3.08

Plant responses to pathogens

Susceptibility: host-pathogens

Resistance: non-host pathogens •Basal defense: first line defense PAMP-triggered immunity(PTI): common pathogen-associated moleculars (lipopolysaccharides, flagellin, elongation factor and peptidoglycans)

•Hypersensive response(HR): Avirulence protein-R protein interaction Effector-triggered immunity(ETI): Type III effetors (T3Es)

Structural class of R proteins

Kruijt M et al. Molecular plant pathology 2005,6( 1 ),85–97

Avirulence and Virulence activity of effectors

Block A et al. Current Opinion in Plant Biology 2008, 11:396–403

Effectors R proteinsHost Targets

Guard Hypothesis

Response to its action instead of Effector itself

1. A R protein could response to two or more unrelated type III effectors targeting the same host machinery.

2. A host protein complex that is a common target of various effctors might be guarded by more than one R protein.

Indirect interaction of Avr-R

Effectors R proteinsHost Targets

One Example

AvrRpm1

AvrB

AvrRpt2

RIN4

Rps2

Rpm1

Induce HR

Couples: AvrB/AvrRpm1-Rpm1 AvrRpt2-Rps2

Yeast two-hybrid and coimmunoprecipitation data shows that:RIN4 directly interacts with AvrB, AvrRpm1 and RPM1

RIN4 is required for the HR induced by RPM1

Col-0: as positive controlRpm1/rps2: double mutant of two R proteins as negative controlrin4-as : homozygous rin4 with normal morphology

Key Experimental Test

Mackey D et al. Cell 2002. 108: 743–754

AvrRpm1 or AvrB Induces RPM1-indepentdent Phosphorylation of RIN4

Key Experimental Test

Mackey D et al. Cell 2002. 108: 743–754

AvrRpt2 induces disappearance of RIN4

Key Experimental Test

Mackey D et al. Cell 2003. 112: 379–389

What does the disappearance do to the interaction of AvrRpt2-RPS2?

Overexpression of RIN4 suppresses RPS2-induced HR

Key Experimental Test

Elimination of RIN4 Activates RPS2:T-DNA insertion into the RIN4 gene is protein null and seedling lethal, while rin4/rps2 double mutants survive

Mackey D et al. Cell 2003. 112: 379–389

Key Experimental Test

AvrRpt2 is sufficient to induce degradation of RIN4

AvrRpt2 could block the function of RPM1 By reducing RIN4

Mackey D et al. Cell 2003. 112: 379–389

Protein

mRNA

avrRpm1-RIN4-Rpm1

avrRps2-RIN4-Rps2

Conclusion

RIN4 is required for the HR induced by both RPM1 and RPS2

AvrRpm1 or AvrB Induces RPM1-indepentdent Phosphorylation of RIN4, and RPM1 recognizes the phosphorylation to induce HR

AvrRpt2 induces disappearance of RIN4, and RPS2 induce HR by the recognization of disappearance

Weak point:

1. Need more convincing evidence from mass spectrometer about the phsophorylation of RIN4 since some other modification may exist;2. Also need RIN4 in Col-0 treated with CIP as a control in following figure a

3.Need pattern of the expression level of RIN4 at different hours without inoculation of effectors in figure b.

a

b

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