Function of the Phytotoxin Coronatine in Pseudomonas Syringae Pathogenesis

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Plant pathogenic bacteria often produce low molecular weight compounds that are involved in virulence or pathogenicity. The research funded by this award involves a phytotoxin called coronatine (COR), a small molecule produced by the plant pathogenic bacterium Pseudomonas syringae pv. tomato (Pst) DC3000. COR plays a critical role in the pathogenesis of Pst DC3000 on tomato and edible plants in the mustard family. However, it is not clear how COR promotes virulence, which is the central question addressed in this project. The interactions between COR and the natural plant growth hormone indole acetic acid (IAA) will be studied by investigating the roles of these two compounds during pathogenesis. Furthermore, biologically active intermediates in the COR biosynthetic pathway will be analyzed for their impact on pathogenesis and plant physiology. The project is anticipated to provide vital new information on the interaction of COR with plant growth hormone pathways and will define whether intermediates in the COR pathway function in pathogenesis. This research approach is innovative and relevant because studies of the plant host, pathogen, and the toxin will be integrated into a multidisciplinary effort utilizing genetics and metabolic profiling. Interest in this project has intensified, largely because COR presumably functions to suppress plant defense responses and as a mimic of the plant hormone jasmonate. The bacterial mutants and plant lines developed in this study will be made freely available to the research community. The project will involve high school students, undergraduates, graduate students, and postdoctoral researchers. The proposed work will establish two new collaborations with experts outside of the field of host-pathogen interactions, and these collaborations will further strengthen ties between the plant pathology and plant biology communities. The proposed work will also benefit society at large through an improved understanding of disease susceptibility and pathogen virulence, possibly leading to improved disease control methods.