Sodium salicylate

Sodium salicylate (NaSal, Fig. 1c), fructose (Fru), glucose (Glc), sorbitol (Sor), sodium hydroxide solution (1, 8 mol L⁻¹), CTAB, sodium dihydrogen phosphate, disodium hydrogen phosphate, alizarin red S (ARS), and trifluoroacetic acid were obtained from FUJIFILM Wako Pure Chemical Co., Osaka, Japan. 3-Fluorophenylboronic acid (3FPBA, Fig. 1d) and 4-fluorosalicylic acid (FSal) were obtained from Tokyo Chemical Industry, Tokyo, Japan. Sodium deuteroxide (NaOD) solution (40% (w/w)) was purchased from Sigma-Aldrich, Tokyo, Japan. Deuterium oxide (D₂O) was acquired from Kanto Chemical Co., Inc., Tokyo, Japan.

Sodium salicylate (Wako, Osaka, Japan), methyl jasmonate (Wako) and ethephon (Sigma‐Aldrich, St Louis, MO, USA), an ET generator, were used as phytohormones. Acetylsalicylic acid (Ac‐SA) (Nacalai Tesque, Kyoto, Japan), 3,5‐dichloroanthranilic acid (DCA) (Tokyo Chemical Industry, Tokyo, Japan), 2,6‐dichlorisonicotianic acid (INA) (Wako) and acibenzolar‐S‐methyl (benzothiadiazole, BTH) (Wako) were used as structural or functional analogs of SA. All phytohormones and chemicals were diluted with water or dimethyl sulfoxide (DMSO). The B. distachyon seedlings or detached leaves were sprayed, soaked or soil‐drenched with a chemical solution containing 0.04% (v/v) Tween 20 and incubated for 24 or 48 h at 23°C. Droplets of chemical solution adhering to the leaf surface were wiped off before the following experiments.

Sodium salicylate (Wako, Osaka, Japan), methyl jasmonate (Wako), and ethephon (Sigma-Aldrich), an ethylene generator, were used. The phytohormones were dissolved in dimethyl sulfoxide (DMSO), then diluted with distilled water to prepare 1 mM solutions (final DMSO concentration is 0.1%), which were supplemented with 0.04% (v/v) tween-20. Four-week-old A. thaliana plants grown on soil were sprayed with the phytohormone solutions and incubated for 48 h at the same growth condition. Then, the detached rosette leaves were prepared and inoculated with R. solani PDA plugs as described above [24 (link)]. For the soil inoculation method, 10-day-old A. thaliana seedlings grown on 1/2MS were sprayed with the phytohormones solutions and kept in the same growth condition for 48 h. Then, seedlings were transplanted in the R. solani-inoculated soil as described before.