Abstract
Systemic acquired resistance (SAR) is a potent innate immunity system in plants that is effective against a broad range of pathogens. SAR development in dicotyledonous plant such as tobacco and Arabidopsis is mediated by salicylic acid (SA). Here, we show that treatment of abscisic acid (ABA) suppressed the induction of SAR in Arabidopsis. Analysis using several mutants in combination with chemicals revealed that treatment of ABA or NaCl suppressed SAR induction by inhibiting both upstream and downstream of SA, independently of JA/ET-mediated signaling pathway. Suppression of ABA-biosynthesis resulted in enhanced SAR induction, indicating that endogenous ABA levels antagonistically regulate SAR induction. Conversely, the activation of SAR suppressed the expression of ABA biosynthesis-related and ABA-responsive genes. Therefore, our data have revealed that antagonistic cross-talk occurs at multiple steps between the SA-mediated signaling of SAR induction and the ABA-mediated signaling of environmental stress responses.
