Transgenic Arabidopsis conditionally expressing the bacterial avrRpm1 type III effector under the control of a dexamethasone-responsive promoter were used for proteomics studies. This model system permits study of an individual effector without interference from additional bacterial components. Coupling of different prefractionation approaches to high resolution 2-DE facilitated the discovery of low abundance proteins - enabling the identification of proteins that have escaped detection in similar experiments. A total of 34 differentially regulated protein spots were identified. Four of these (a remorin, a protein phosphatase 2C (PP2C), an RNA-binding protein, and a C2-domain-containing protein) are potentially early signaling components in the interaction between AvrRpm1 and the cognate disease resistance gene product, resistance to Pseudomonas syringae pv. maculicola 1 (RPM1). For the remorin and RNA-binding protein, involvement of PTM and post-transcriptional regulation are implicated, respectively.