Figure 1.
UV-B priming system. (a) Conceptional model of the UV-B priming system. The plant material of all treatments is harvested to one time point (Sampling). Priming: A gene is primed if its expression is significantly higher after double treatment (+/+) than without priming (1st) treatment (-/+), whereas primed plants show reduced damage. (b) Percentage of plants with at least one damaged primary leaf dependent of the duration (min, minutes) of a single high dose UV-B treatment; N = 9. (c-f) Damage of Col-0 (c,e) and uvr8-6 primary leaves (d,f) exposed to the four treatments of the UV-B priming system four days after UV-B second treatment (high dose). The plants were classified into four damage categories (e,f); N ≥ 12 (Col-0) or 4 (uvr8-6). (g-o) Damage of Col-0 primary leaves exposed to the four treatments, five days after the second UV-B treatment (low dose). Arrow heads mark lesions in leaf surface. (g) N = 9. (l-o) False color images of (h-k). (p) Pigment accumulation in Col-0 plants exposed to the four treatments, seven days after second UV-B treatment (low dose). Equal treated plants displayed similar colored leaves, whereas -/+ and +/+ plants were not distinguishable (N = 10 plants, each treatment). (q) Quantitative RT-PCR analyses of mRNA expression in seedlings (17 DAG, 3 hours after 2nd treatment) normalized by eIF4. The expression levels are indicated as the mean of relative fold changes of three biological replicates; values are scaled to -/- = 1; the black bars represent the standard errors. (r-s) Damage of primary leaves of Col-0 (N = 17) and npr1-1 plants (N = 15) exposed to UV-B priming treatment three days after UV-B second treatment (+, high dose). Note the limited damage of one primary leaf in Col-0 + in comparison to the necrotic leaves in npr1-1 + (arrow heads). (s) Detached primary leaves of the plant in (R, npr1-1 +). (a-s) Asterisks indicate significant changes in comparison to -/-, whereas the blue asterisks indicate significant changes between -/+ and +/+ (Student’s t test: #, P = .06; *, P ≤ 0.05; **, P ≤ 0.01; ***, P ≤ 0.001). All scale bars = 2 mm