Abstract
We employed chemical biology approach to understand salicylic acid (SA)-mediated disease resistance responses in plants. A high-throughput chemical screening that monitors hypersensitive responses (HR) of Arabidopsis suspension cells infected by Pseudomonas syringae pv. tomato DC3000 (Pst) avrRpm1, identified 7 chemicals named CB which enhance the HR cell death. Here we show the target identification of four of these CB compounds. CB_8 and CB_9 possess common structural skeleton and CB_11 and CB_12 share the same motif. These CBs conferred resistance to Arabidopsis plants against both virulent and avirulent Pst strains. They do not have SA-analog activity but enhanced defense responses during pathogen infection. Then, the chemical effects on SA-inactivating pathway were examined. We found that CB_8, CB_9, CB_11 and their derivatives inhibited the enzymatic activity of UGT74F1, a major SA glucosyltransferase (SAGT). The concentration ranges of them for SAGT inhibition coincided with those for HR enhancement. The knockout line of At2g43840 gene for UGT74F1 showed enhanced disease resistance, indicating the usefulness of SAGT as a target for plant protection technologies.
