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Lecture 3

Lecture 3 Summary

Cell and Systems Biology
Course Code
Darrel Desveaux

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ETI Gene for Gene Resistance
Plant R-protein recognizes specific bacterial Avr protein, which lead to HR. TTSE = Hop and block HR.
Many R proteins are CC/TIR-NB-LRR, Kinase or TF. May be membrane bound.
Compatible = virulent, unrecognizable by plant defence = susceptible, diseased plant.
Incompatible = avirulent, recognizable by plant defence = resistant plant. Resistance is a dominant trait.
Different soybean cultivars recognize different TTSE: Merit recognizes AvrB, not AvrRpm1, as AvrB-
grows better. Flambeau recognizes AvrRpm1 but not AvrB as AvrRpm1- grows better.
Both AvrB and AvrRpm1 recognition is mapped to Rpg1 locus containing Rpm1 protein.
Rpm1-null plant has no HR and later die of disease.
Lock model: R protein is receptor and TTSE is ligand, only 2 examples. AvrPita: Pita and Avr9: Cf9.
RPM1 Interacting Protein (RIN4)
Guard model: R protein monitor TTSE target by directly binding to targets.
RIN4 is targeted by both AvrB and AvrRpm1 and bound by R protein RPM1 and is necessary for
recognition of AvrB and AvrRpm1 by RPM1 as in rin4 KD there is no HR.
AvrB and AvrRpm1 induce RIN4 phosphorylation. RPM1 recognize phosphor ylation and induce HR.
AvrRpt2 protease targets RIN4 by cutting it into 3 pieces (disappear). AvrRpt2 is recognized by RPS2.
AvrRpt2 block AvrB/AvrRpm1 recognition of RIN4 to prevent phosphorylation of RIN4, which is
recognized by RPM1 and triggers HR.
AvrRpt2 promote virulence even when RIN4 is absent, so there are other targets.
Cannot recover
-/- plants but can recover
-/- plants because in
-/- plants RPS2
induces HR that kills the plant.
RIN4 is a negative regulator of basal defence and TTSE t arget RIN4 to suppress basal defence.
2-/- pant show less callose deposit (less PTI).
Overexpressing RIN4 reduce PTI callose when treated with f lg22.
Plants overexpressing AvrRpm1 also has less callose, so phosphorylation of RIN4 may activate it.
Therefore it seems bacteria benefit no matter RIN4 is present or absent.
Also RIN4 is needed for
Pseudomonas syringae
to reopen closed stomata.
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