Discovering the plant cellular targets of P. syringae virulence factor AvrPpiB

University Of North Carolina At Chapel Hill, Chapel Hill NC

Investigators

Abstract

The goal of the proposed research is to characterize proteins that interact with type III effectors, using the Arabidopsis- P. syringae interaction as a model pathosystem. One type III effector, the Pseudomonas syringae AvrPpiB protein, has no known or predicated biochemical function. However, preliminary data have shown that this factor increases bacterial growth by 10-fold under mild water deficit conditions when introduced into a bacterial strain with reduced virulence. AvrPpiB also causes systemic chlorosis when expressed in older leaves of Arabidopsis. These observations suggest that AvrPpiB plays a physiological role in microbes and plants. Several objectives are proposed to understand the precise function of AvrPpiB. First, ecotype differences in AvrPpiB-dependent host responses will be mapped as a prelude to positional cloning of the responsible genes. Second, a mutant screen will be undertaken to identify host (Arabidopsis) genes that are required for AvrPpiB-dependent host responses. The mutants will be characterized using physiological, biochemical, and "-omics" technologies, and potentially informative genes will be cloned. Third, changes in transcription profiles will be assessed in Arabidopsis that either respond or fail to respond to AvrPpiB. This should provide insight into signaling pathways that give rise to the response. Fourth, proteins that interact with AvrPpiB will be identified in vitro using yeast expression assays, and in vivo by expressing TAP-tagged effector protein fusions in Arabidopsis and purifying tagged protein complexes. Broader Impacts: This project will add to our understanding of host components that interact or mediate plant response to bacterial pathogens. This has implications for the design of resistant crop species. The proposed research will also involve undergraduates, graduate students, and postdoctoral fellows, including minorities. Outreach activities will be undertaken that relate to educating the public on issues about genetically modified foods.