P-053 - Long-distance defence signalling is modulated by jasmonic acid and abscisic acid in Arabidopsis thaliana.

Systemic Acquired Resistance (SAR) is a mechanism whereby pathogen induced local activation of host resistance proteins (Effector Triggered Immunity, ETI) induces broad-spectrum systemic protection. Salicylic acid (SA) is classically associated with induction of SAR almost at the exclusion of other hormones. Here, we demonstrate a concerted role for jasmonic acid (JA), abscisic acid (ABA), electrical and calcium signalling in the early stages of SAR signal propagation and translocation. Using the JASMONATE-INDUCED SYSTEMIC SIGNAL 1 (JISS1) promoter, temporal-spatial dynamics of ETI-elicited SAR signalling were monitored at the whole plant and subcellular levels. JISS1:LUC signalling was observed following challenge with ETI-inducing strains of Pseudomonas syringae pv. tomato strain DC3000 (DC), and JISS1 expression was rapidly upregulated in systemic tissue. Pre-treatment with ABA prior to challenge abolished JISS1:LUC induction. JISS1:LUC signalling was unaffected in SA mutants, but was lost in JA mutants. JISS1:LUC signalling was observed in response to wounding and the fungal pathogen Sclerotinia sclerotiorum. Mirroring JA-dependent wounding responses, ETI-activated electrical surface potentials were dependent on JA signalling and JISS1. Collectively, our results indicate that the phytohormone signalling landscape during SAR induction is more intertwined than previously thought, and that JA, but not SA, is crucial for JISS1-mediated systemic defence to DC in A. thaliana.