Poster: Plant Pathogen/Symbiont Interactions

Abs # 749: Characterization of Arabidopsis thaliana expressing AvrPphE_Pto, a type III effector of Pseudomonas syringae pv. tomato DC3000

Presenter:	Bandyopadhyay, Sruti , bandyopa@msu.edu
Authors	Bandyopadhyay, Sruti  (A)   He, Sheng Yang  (A)
Affiliations:	(A): Michigan State University

Pseudomonas syringae pv. tomato DC3000 (Pst DC3000) is a virulent pathogen of Arabidopsis thaliana. The type III secretion system (TTSS), encoded by the hrp (hypersensitive response and pathogenicity) genes, is crucial to pathogenesis because hrp mutants (e.g., hrpS and hrcC [formerly hrpH] mutants) of Pst DC3000 are unable to multiply or cause disease in compatible hosts. Pst DC3000 utilizes the TTSS to secrete and translocate numerous effector proteins which collectively function to modulate host cellular processes and cause disease development. Many effector proteins were initially identified as mediators of gene-for-gene resistance responses and named Avr proteins. Increasing evidence supports dual functions for many Avr proteins as recognition determinants in resistant hosts and virulence determinants in susceptible hosts. Three new effectors were identified by screening a cosmid library of Pst DC3000 using ten known P. syringae avr genes as probes. These are similar to virPphA and avrPphE from Pseudomonas syringae pv. phaseolicola, and avrPpiB from Pseudomonas syringae pv. pisi respectively. All three effectors were shown to be translocated in a type III dependent manner using the avrRpt2-based HR assay. Like many other effectors, insertional inactivation of these genes did not cause a loss of virulence. In order to investigate the contribution of an individual effector protein, we expressed avrPphE_Pto in Arabidopsis thaliana under the control of an inducible promoter. Characterization and expression profiling analysis of these transgenic plants will be presented.