Abstract
Systemic acquired resistance (SAR) is a potent innate immunity system in plants that is induced through the salicylic acid (SA)-mediated signaling pathway. Here, we characterized 3-chloro-1-methyl-1H-pyrazole-5-carboxylic acid (CMPA) as an effective SAR inducer in Arabidopsis. The soil drench application of CMPA enhanced a broad range of disease resistance against the bacterial pathogen Pseudomonas syringae and fungal pathogens Colletotrichum higginsianum and Botrytis cinerea in Arabidopsis, whereas CMPA did not show antibacterial activity. Foliar spraying with CMPA induced the expression of SA-responsible genes such as PR1, PR2 and PR5. The effects of CMPA on resistance against the bacterial pathogen and the expression of PR genes were observed in the SA biosynthesis mutant, however, while they were not observed in the SA-receptor-deficient npr1 mutant. Thus, these findings indicate that CMPA induces SAR by triggering the downstream signaling of SA biosynthesis in the SA-mediated signaling pathway.