Abstract
Systemic acquired resistance (SAR) is a potent innate immunity system in plants that is effective against a broad range of pathogen. SAR development in dicotyledonous plants such as tobacco and Arabidopsis is mediated by salicylic acid (SA). Here, using different types of SAR-inducing chemicals, i.e., 1, 2-benzisothiazol-3(2H)-onel, 1-dioxide (BIT) and benzo (1,2,3) thiadiazole-7-carbothioic acid S-methyl ester (BTH) that act on upstream and downstream of SA in the SAR signaling pathway, respectively, we show that treatment of abscisic acid (ABA) suppresses the induction of SAR in Arabidopsis. In our previous studies, it was indicated that ABA suppressed PR genes expression and SA accumulation induced by BIT or BTH. Moreover, ABA suppressed PR genes expression in BTH-treated sid2 mutant, defective in SA biosynthesis, suggesting that ABA suppressed both upstream and downstream of SA in SAR signaling pathway. To clarify SAR suppression mechanism of SAR by ABA, we performed microarray analysis.
