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Oral: Role of Phytobiomes in Plant Disease Control


The role of insect-associated microbes in altering host plant defenses.
C. CASTEEL (1), A. Bak (2), S. Whitham (3) (1) University of California-Davis, U.S.A.; (2) University of California - Davis, U.S.A.; (3) Iowa State University, U.S.A.

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Plants employ diverse responses mediated by phytohormones to defend themselves against pathogens and herbivores. Adapted pathogens and herbivores often manipulate these responses to their benefit. Previously we demonstrated that Turnip mosaic virus (TuMV) infection suppresses callose deposition, an important plant defense induced in response to feeding by its aphid vector (Myzus persicae), and increases aphid fecundity compared to uninfected control plants. We determined that production of a single TuMV protein, NIa-Pro (Nuclear Inclusion a - Protease domain), was responsible for decreased plant defenses through changes in the phytohormone signaling molecule ethylene. Further, we show NIa-Pro reversibly responds to the presence of the aphid vector during infection, relocalizing from the nucleus to the vacuole. Importantly, relocalization is required for NIa-Pro’s ability to decrease plant defense and this phenomenon occurs for other potyviruses. Taken together, these results suggest that the virus responds to the presence of the insect vector, promoting insect performance and transmission through host plant changes only when needed, a phenomenon that has not been previously demonstrated for any animal or plant viruses.