Fig. 5

Verification of identified priming compound in soil grown A. thaliana plants. A Tyr020 primes A. thaliana plants for enhanced WRKY6 and WRKY53 defense gene activation. Six-week-old plants remained untreated (-) or sprayed with wettable powder ( +) or the indicated concentration of Tyr020 in wettable powder (WP) ( +) before they were elicited ( +) or not (-) with flg22. As positive control 100 µM Benzothiadiozole (BTH) was used. The accumulation of WRKY6 and WRKY53 mRNA transcript was determined by qRT-PCR. Stars (*) indicate significant differences between control (WP; +) and sample (p ≤ 0.05). B Sulforaphane (SFN) reduces downy mildew disease. Plants were treated with WP or a WP formulation of Tyr020 (25 µM). Twenty-four hours later, we spray-inoculated plants with a suspension of Hyaloperonospora arabidopsidis (Hpa) conidiospores (4 × 10⁴ spores per mL of water). Inoculated plants were kept at high humidity in short day. After 7 d, we determined the number of spores released by Hpa. Data were analyzed by Student’s t test. Asterisk denotes a statistically significant difference with 95% confidence. Data presented are means ± SD. n > 5. C A. thaliana seedlings pretreated with Tyr020 have enhanced phosphorylation of mitogen-activated protein kinase (MPK) activation motifs upon flg22 challenge. This indicates stronger MPK activation in Tyr020-pretreated plants. As positive control A. thaliana seedlings were treated with 50 µM salicylic acid (SA)