Mechanisms Underlying Robustness and Tunability in a Plant Immune Signaling Network

• A predictive, dynamic PTI signaling network model with four major sectors was built
• Inhibition of the jasmonate sector by the ethylene sector was central to robustness
• MAMP-specific patterns of multiple inputs can tune the network response
• The symmetrically placed jasmonate and PAD4 sectors may form a tetrastable switch

SummaryThe plant immune signaling network needs to be robust against attack from fast-evolving pathogens and tunable to optimize immune responses. We investigated the basis of robustness and tunability in the signaling network controlling pattern-triggered immunity (PTI) in Arabidopsis. A dynamic network model containing four major signaling sectors, the jasmonate, ethylene, phytoalexin-deficient 4, and salicylate sectors, which together govern up to 80% of the PTI levels, was built using data for dynamic sector activities and PTI levels under exhaustive combinatorial sector perturbations. Our regularized multiple regression model had a high level of predictive power and captured known and unexpected signal flows in the network. The sole inhibitory sector in the model, the ethylene sector, contributed centrally to network robustness via its inhibition of the jasmonate sector. The model’s multiple input sites linked specific signal input patterns varying in strength and timing to different network response patterns, indicating a mechanism enabling tunability.

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