Poster: Plant Pathogen/Symbiont Interactions

Abs # 725: Characterization of Arabidopsis thaliana plants that express AvrPto of Pseudomonas syringae pv. tomato DC3000

Presenter:	Hauck, Paula M., leepaul1@msu.edu
Authors	Hauck, Paula M. (A)   Thilmony, Roger  (A)   He, Sheng Yang  (A)
Affiliations:	(A): DOE Plant Research Laboratory, Michigan State University

Although much research has focused on disease resistance mechanisms, the molecular basis of plant susceptibility to pathogen infection remains elusive. We are investigating the susceptibility of Arabidopsis to the bacterial pathogen Pseudomonas syringae pv. tomato strain DC3000 (DC3000). DC3000 causes speck disease, characterized by water-soaking, chlorosis, and necrosis in the infected leaves. DC3000 is believed to deliver numerous effector proteins, via the type III secretion system, into host cells to promote disease. Some of these type III effector proteins act as avirulence factors in resistant plants. One of the most extensively characterized avirulence factors is AvrPto, which activates Pto-dependent resistance responses in tomato. The role of AvrPto in susceptible Arabidopsis has not yet been determined. One method for determining the role of AvrPto in a susceptible host is the creation and analysis of transgenic plants that express this bacterial protein. Several Arabidopsis lines expressing AvrPto under an inducible promoter have been generated. Microarray analysis shows that the gene expression pattern of plants expressing AvrPto is similar to that of plants infected by DC3000. In addition, AvrPto, compromises defense-related callose deposition in the host cell wall, and permits substantial multiplication of a DC3000 type III secretion mutant. These results suggest that AvrPto is a member of a class of type III effectors which target a cell wall-based defense to modulate plant susceptibility.