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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
Indirect interaction of Avr-R
Guard Hypothesis
Host Targets
Effectors
R proteins
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.
One Example
Host Targets
Effectors
R proteins
RIN4
Rpm1
AvrB
AvrRpm1
Rps2
AvrRpt2
Induce HR
Couples: AvrB/AvrRpm1-Rpm1
AvrRpt2-Rps2
Key Experimental Test
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 control
Rpm1/rps2: double mutant of two R proteins as negative control
rin4-as : homozygous rin4 with normal morphology
Mackey D et al. Cell 2002. 108: 743–754
Key Experimental Test
AvrRpm1 or AvrB Induces RPM1-indepentdent Phosphorylation of RIN4
Mackey D et al. Cell 2002. 108: 743–754
Key Experimental Test
AvrRpt2 induces disappearance of RIN4
What does the disappearance do to
the interaction of AvrRpt2-RPS2?
Mackey D et al. Cell 2003. 112: 379–389
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
Overexpression of RIN4 suppresses RPS2-induced HR
Mackey D et al. Cell 2003. 112: 379–389
Key Experimental Test
AvrRpt2 is sufficient to induce degradation of RIN4
Protein
mRNA
avrRpm1-RIN4-Rpm1
avrRps2-RIN4-Rps2
AvrRpt2 could block the function of RPM1
By reducing RIN4
Mackey D et al. Cell 2003. 112: 379–389
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
a
b
3.Need pattern of the expression level of RIN4
at different hours without inoculation of
effectors in figure b.
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