Abstract
We are using a chemical biology approach to investigate Arabidopsis R-gene mediated disease resistance mechanism to the bacterial pathogen Pseudomonas syringae pv. tomato DC3000 avrRpm1. A high-throughput screening method for hypersensitive responses (HR) using suspension cells was established and seven compounds that enhanced HR cell death were identified from a library of 10,000 diverse chemicals. One of these HR potentiators, CB_6, induced expression of PR1 gene in Arabidopsis seedlings of both wild-type and sid2 mutant, indicating that CB_6 works as an analog of SA. CB_6 did not affect endogenous SA levels, suggesting that CB_6 is not involved in the positive feedback regulation of SA. Unlike SA, CB_6 did not suppress LOX2 gene expression induced by jasmonic acid (JA), suggesting that CB_6 does not possess antagonistic effect to JA signaling. To identify target protein of CB_6, we isolated 14 Arabidopsis sgi (SA agonist insensitive) mutants and their map-based cloning procedures are being carried out. We are also trying to employ two other different approaches for identification of CB_6 binding protein using biotinylated probe and yeast three-hybrid system.
