Summary Salicylates including salicylic acid (SA) are one of the major defense-signaling hormones (jasmonates are the others). Plants that are deficient in SA synthesis or signaling are much more susceptible to many microbial pathogens, particularly biotrophic or hemibiotrophic pathogens. SA accumulates upon pathogen infection, leading to the transcriptional induction of a very large number of disease associated genes. Many gaps remain in our understanding of this crucial but complex signaling pathway, not the least of which is the identity of the SA receptor(s).