Fig. 2: GSH triggers [Ca²⁺]_cyt propagation and defense gene expression in systemic leaves.

a [Ca²⁺]_cyt fluorescence signal imaging of GCaMP3 plants after 100 mM GSH, Glu, and sorbitol (sorb) application to leaf 1 (L1) (white arrow, 0 s) respectively. White arrowheads (200 s, 400 s) indicate leaf 6 (L6) and leaf 3 (L3). Scale bars: 2 mm. b Schematic diagram for application of small molecule to the cut edge of damaged leaf 1. Small molecule was added to the cut edge of the damaged leaf 30 min after wounding for assessment of small molecules-induced Ca²⁺ signal transmission. In contrast, a longer recovery period of 5 h post pre-cutting was required for the assessment of small molecules-activated gene expression levels. c, d Quantitative measurement of [Ca²⁺]_cyt levels (c) and expression levels of defense genes (d) in target leaf 6 at indicated times after application of 100 mM GSH, Glu, and sorbitol to leaf 1 of GCaMP3 plants. Data are mean ± SD (n = 3, 9, 9 for sorbitol, GSH and Glu treatment in c, n = 3 for d). Statistical significance was determined by Dunnett’s test. e [Ca²⁺]_cyt fluorescence signal imaging of GCaMP3 plants pretreated with LaCl₃ or Silwet-L77 after 100 mM GSH application to leaf 1 (L1) (white arrow, 0 s). White arrowhead (400 s) indicates leaf 6 (L6). Scale bars: 2 mm. f Schematic diagram of LaCl₃ pretreatment before GSH treatment. LaCl₃ (50 mM) was added to a strip of Kimwipes laid over the petiole of leaf 1 (L1). 0.05% (v/v) Silwet-L77 was added as a wetting agent to improve LaCl₃ penetration of the cuticle. g, h Quantitative measurement of [Ca²⁺]_cyt levels (g) and defense gene induction (h) in target leaf 6 after application of 100 mM GSH to leaf 1 of GCaMP3 plant pretreated with LaCl₃ or Silwet-L77 at indicated times. Data are mean ± SD (n = 5 for g, n = 3 for h). Statistical significance was determined by two-sided Welch’s t-test. Source data are provided as a Source Data file.