Targets of the Type III Effector AvrRpt2 from the Phytopathogenic Bacterium Psuedomonas syringae (2006)

Undergraduate: Priyesh Patel

Faculty Advisor: Jeff Dangl
Department: Biology

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Thirty percent of crops grown annually are lost to disease. Therefore, gaining insight into the pathogenic and immunological factors governing plant disease and resistance is scientifically and economically important. The phytopathogen Pseudomonas syringae infects the model plant Arabidopsis thaliana using virulence proteins that it injects directly into host cells to promote disease. Interestingly, A. thaliana plants contain resistance proteins that recognize a group of these pathogenic proteins known as avirulence proteins. This recognition is very specific?a given resistance protein can recognize only specific avirulence proteins. Recognition of a bacterial avirulence protein by a resistance protein leads to cell death at the site of bacterial infection known as the hypersensitive response. This localized cell death limits bacterial growth, which prevents bacteria from infecting the entire plant.
The bacterial avirulence protein AvrRpt2 activates the A. thaliana resistance protein RPS2, thereby inducing localized cell death. RIN4 is an A. thaliana protein that interacts with RPS2 and prevents it from promoting cell death. AvrRpt2 is a protease that cleaves itself to its active form inside the plant cell. RIN4 contains two possible AvrRpt2 cleavage sites. For my project, I demonstrated that AvrRpt2 cleaves RIN4 in vitro and in vivo. I also proposed a model to explain how RPS2 recognizes AvrRpt2 activity by monitoring the degradation of RIN4.