Fig. 4: eNAD(P) is a potential mobile SAR signal.

a, b SAR induction-triggered systemic accumulation of eNAD(P). The eNAD(P) levels were assessed by analyzing apoplastic washing fluids (AWFs) of the indicated leaves. Three lower leaves on each wild-type plant were infiltrated with Psm (+SAR) or 1 mM MgCl₂ (-SAR). One upper systemic leaf on each plant was collected at the indicated times. Values are expressed relative to the eNAD(P) levels in -SAR samples at 24 h, which were arbitrarily set to 1, allowing comparison across experiments. Bars represent means ± SE (n = 3 independent AWF samples). SAR induction caused significant eNAD(P) accumulation in the systemic leaves (one-way ANOVA with Tukey’s test). The experiment was repeated with similar results. c, d SAR induction-triggered systemic accumulation of eNAD(P) in wild type (WT) and fin4-3 at 48 h after the induction. Values are expressed relative to the eNAD(P) levels in WT/-SAR samples, which were arbitrarily set to 1. Bars represent means ± SE (n = 3 independent AWF samples). The SAR induction-induced systemic eNAD(P) accumulation was significantly reduced in fin4-3 (one-way ANOVA with Tukey’s test). The experiment was repeated with similar results. e NAD(P)⁺-induced systemic immunity in WT and fin4-3. Bars represent means ± SE (n = 8 independent leaf disks). NAD(P)⁺ induced similar levels of systemic immunity in the WT and fin4-3 plants (two-tailed t test). The photo was taken 72 hpi. The experiment was conducted three times with similar results. f GUS expression in Dex-infiltrated lower leaves and upper noninfiltrated systemic leaves of Dex:FIN4/fin4-3 plants. Leaves were collected 24 h after the treatment. g Morphology of three-week-old plants of the indicated genotypes treated with 1 μM Dex or water (-Dex) by soil drenching every other day after transplanting. h, i SAR induction-triggered systemic accumulation of eNAD(P) in Dex:FIN4/fin4-3 plants with lower leaves being pretreated with or without Dex. Three lower leaves on each plant were infiltrated with 50 μM Dex or 0.1% methanol (-Dex). Twenty-four hr later, biological induction of SAR was conducted. The upper systemic leaf was collected 48 h later and AWFs were then extracted. Values are expressed relative to the eNAD(P) levels in the -Dex/-SAR samples, which were arbitrarily set to 1. Bars represent means ± SE (n = 3 independent AWF samples). SAR induction induced the movement of significant amounts of eNAD(P) from the Dex-treated lower leaves to the upper systemic leaves of the Dex:FIN4/fin4-3 plants (one-way ANOVA with Tukey’s test). The experiment was repeated with similar results. j, k Biological induction of SAR in the indicated genotypes with lower leaves being pretreated with or without Dex. Three lower leaves on each plant were infiltrated with 50 μM Dex or 0.1% methanol (-Dex). Twenty-four hr later, biological induction of SAR was determined. 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). The photo (k) was taken 72 hpi. The experiment was performed three times with similar results.