Abstract
Salicylic acid (SA) plays important roles both in the hypersensitive response and in the systemic acquired response (SAR). Two pathways are proposed for the biosynthesis of SA in Arabidopsis: the benzoic acid (BA) pathway and the isochorismate pathway. In the latter, a mutant defective in isochorismate synthase has been isolated and this mutant is known to be involved in SAR. However, mutants related to the former pathway have not been identified. To study the BA pathway in plant immune responses, we isolated the BA-sensitive mutant bah1 (benzoic acid hypersensitive 1). The bah1 mutant accumulated high levels of SA and expressed the PR1 gene after the application of BA, suggesting that the BA pathway for SA biosynthesis is activated in the bah1 mutant. Moreover, the bah1 mutant was resistant to Pseudomonas syringae.
