Characterization of plant immunity-activating mechanism by a pyrazole derivative.

A newly identified chemical, 4-{3-[(3,5-dichloro-2-hydroxybenzylidene)amino]propyl}-4,5-dihydro-1H-pyrazol-5-one (BAPP) was characterized as a plant immunity activator. BAPP enhanced disease resistance in rice against rice blast disease and expression of a defense-related gene without growth inhibition. Moreover, BAPP was able to enhance disease resistance in dicotyledonous tomato and Arabidopsis plants against bacterial pathogen without growth inhibition, suggesting that BAPP could be a candidate as an effective plant activator. Analysis using Arabidopsis sid2-1 and npr1-2 mutants suggested that BAPP induced systemic acquired resistance (SAR) by stimulating between salicylic acid biosynthesis and NPR1, the SA receptor protein, in the SAR signaling pathway.