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Network analysis to uncover and quantify host defense signaling-dependent virulence effects of Pseudomonas syringae pv. tomato

Alex Turo: Ohio State University

<div>Interactions between plants and phytopathogenic bacteria are dynamic, with outcomes that depend on the interactions of virulence effectors and host defense pathways. Among the arsenal of effectors of <em>Pseudomonas syringae </em>pv. <em>tomato</em> (<em>Pto</em>), the phytotoxin coronatine (COR) and the functionally redundant type-III effectors AvrE1 and HopM make key contributions to virulence on host plants. While these effectors perform partially overlapping functions by interacting with distinct host targets, an understanding of how their activities are coordinated through downstream pathways is unclear. <em>Arabidopsis thaliana</em> employs a hormone-dependent signaling network to coordinate host defense, including against <em>Pto</em>. COR, AvrE1 and HopM1 directly and indirectly target the salicylic acid, jasmonate, ethylene, and indole glucosinolate-dependent sectors of this network. We have constructed polymutant sets of both Pto and Arabidopsis for all combinations of these effectors and pathways and will measure quantitatively the interaction of these strains and plants, at both the level of bacterial growth and plant responses. This approach will enable network reconstitution to reveal the virulence contributions of individual and interacting effectors in the context of plants disrupted in different sectors of the hormone network. By determining virulence effector activity in the context of the host defense network, we aim to better understand effector-dependent mechanisms of virulence.</div>