Fig. 2: NAD(P)⁺ is a strong immune activator in the extracellular space.

a, b NAD(P)⁺-induced local immunity in wild type (WT) and fin4-3. Two leaves on each plant were infiltrated with 0.2 mM NAD⁺, 0.4 mM NADP⁺, or water. Four hr later, the infiltrated leaves were inoculated with Psm. Photos in (a) and samples in (b) were taken 72 hpi. Bars in (b) represent means ± SE (n = 8 independent leaf disks). Asterisks denote significant differences between NAD(P)⁺- and water-treated samples (two-tailed t test; p values are shown in the Source Data file). The experiment was conducted three times with similar results. c, d Total NAD (including intracellular and extracellular NAD) levels (c) and induction of FRK1, ALD1, and FMO1 (d) in WT and fin4-3 treated with NA or NAD⁺. Two leaves on each plant were infiltrated with 4 mM NA, 0.2 mM NAD⁺ or water. The infiltrated leaves were collected 4 h later. Bars represent means ± SE (n = 3 independent leaf samples (c) or total RNA samples (d)). Different letters denote significant differences (one-way ANOVA with Tukey’s test; p values are shown in the Source Data file). The experiments were repeated with similar results. e, f NA- and NAD⁺-induced local (e) and systemic (f) immunity in WT and fin4-3. Two (e) or three leaves (f) on each plant were infiltrated with the indicated concentrations of NA, NAD⁺ or water. Four hr later, either the infiltrated leaves (e) or one upper systemic leaf (f) was inoculated with Psm. Samples were taken 72 hpi. Bars represent means ± SE (n = 8 independent leaf disks). Different letters denote significant differences (one-way ANOVA with Tukey’s test; p values are shown in the Source Data file). RLU relative light unit. The experiments were performed three times with similar results.