A BENZOTHIADIAZOLE DERIVATIVE INDUCES SYSTEMIC ACQUIRED-RESISTANCE INTOBACCO

Systemic acquired resistance (SAR) is a pathogen-induced disease resis tance response in plants that is characterized by broad spectrum disea se control and an associated coordinate expression of a set of SAR gen es. Benzo(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH) i s a novel synthetic chemical capable of inducing disease resistance in a number of dicotyledenous and monocotyledenous plant species. In thi s report, the response of tobacco plants to BTH treatment is character ized and the fact that it controls disease by activating SAR is demons trated. BTH does not cause an accumulation of salicylic acid (SA), an intermediate in the SAR signal transduction pathway. As BTH also induc es disease resistance and gene expression in transgenic plants express ing the nahG gene, it appears to activate the SAR signal transduction pathway at the site of or downstream of SA accumulation. BTH, SA and T MV induce the PR-1a promoter using similar cis-acting elements and gen e expression is blocked by cycloheximide treatment. Thus, BTH induces SAR based on all of the physiological and biochemical criteria that de fine SAR in tobacco.