In plants, effector-triggered immunity (ETI) in the local tissue can lead to long-lasting, broad-spectrum systemic acquired resistance (SAR) through production of the immune inducer salicylic acid (SA). However, 90 years after report of its observation, the initiating mobile signal and its transduction mechanism leading to systemic SA synthesis and how SA activates broad-spectrum disease resistance in naïve tissue are not completely understood. In my talk, I report recent discoveries made in my lab in addressing these questions.