Masanori Nishioka

N-Cyanomethyl-2-chloroisonicotinamide Induces Systemic Acquired Resistance in Arabidopsis without Salicylic Acid Accumulation

Systemic acquired resistance (SAR) is a potent innate immunity system in plants that is induced through the salicylic acid-mediated pathway. N-cyanomethyl-2-chloroisonicotinamide (NCI) is able to induce a broad range of disease resistance in tobacco and rice and induces SAR marker gene expression without SA accumulation in tobacco. To clarify the detailed mode of action of NCI, we analyzed its ability to induce defense gene expression and resistance in Arabidopsis mutants that are defective in various defense signaling pathways. Wild-type Arabidopsis treated with NCI exhibited increased expression of several pathogenesis-related genes and enhanced resistance to the bacterial pathogen, Pseudomonas syringae pv. tomato DC3000. NCI induced disease resistance and PR gene expression in NahG transgenic plants, but not in the npr1 mutant. NCI could induce PR gene expression in the etr1-1, ein2-1 and jar1-1 mutants. Thus, NCI activates SAR, independently from ethylene and jasmonic acid, by stimulating the site between SA and NPR1.

Pyrazolecarboxylic Acid Derivative Induces Systemic Acquired Resistance in Tobacco

Systemic acquired resistance (SAR) is a potent innate immunity system in plants that is induced through asalicylic acid (SA)-mediated pathway. Here, we characterized 3-chloro-1-methyl-1H-pyrazole-5-carboxylic acid (CMPA) as an effective SAR inducer in tobacco. Soil drench application of CMPA induced PR gene expression and a broad range of disease resistance without antibacterial activity in tobacco. Both analysis of CMPAs effects on NahG transgenic tobacco plants and SA measurement in wild-type plants indicated that CMPA-induced resistance enhancement does not require SA. Therefore, it is suggested that CMPA induces SAR by triggering the signaling at the same level as or downstream of SA accumulation as do both benzo(1,2,3)thiadiazole-7-carbothioic acid S-methyl ester and N-cyanomethyl-2-chloroisonicotinamide.