Figure 1.

Coumaroylagmatine Accumulates Extracellularly in Arabidopsis, But Not in Potato, and Inhibits P. infestans Spore Germination in Vitro.

(A) and (B) Coumaroylagmatine content of leaves (A) and in droplets of the inoculum (B) from Arabidopsis and potato plants 24 h after inoculation with P. infestans. Data shown were obtained in at least five independent experiments (Arabidopsis, n ≥ 107; potato, n = 56). Error bars represent se. Significance analysis of differences was performed by t test, ***P < 0.001. fw, fresh weight.

(C) Mycelial growth inhibition assays. Coumaroylagmatine was added to GFP-expressing P. infestans (isolate Cra208m2) mycelium at the indicated concentrations. GFP fluorescence was determined at the time points indicated (control, n = 5; 1 mM, n = 10; 10 mM, n = 9). Data shown are representative for at least three independent experiments.

(D) Spore germination inhibition assay. Coumaroylagmatine was added to a P. infestans zoospore suspension (10⁵/mL⁻¹) at the indicated concentrations. After 24 h, the samples were evaluated microscopically for spore germination. Data are derived from two independent experiments (n = 4). Significance analysis of differences was performed by t test, *P < 0.05 and ***P < 0.001.