In the most recent issue of  Cell Reports, Yue Wu and  seven other associates at the Dept. of Biological Sciences, Brock University  Ontario, Canada have described salicylic acid (SA) as an essential hormone in plant immunity. Little is hitherto known about the receptor of this essential hormone. The authors have  demonstrated that NPR1 (Natriuretic Peptide Receptor 1)  directly binds SA. It has an affinity similar to that of other hormone-receptor interactions and consistent with in vivo Arabidopsis SA concentrations. Furthermore they showed that binding of SA occurs through Cys521/529 via the transition metal copper. Mechanistically, their results advocate that binding of SA causes a conformational change in NPR1.  They further showed that this reaction  is accompanied by the release of the C-terminal transactivation domain from the N-terminal autoinhibitory BTB/POZ domain. These authors suggest for the first time, that NPR1 is the receptor for SA.