Figure 1.

HPCA1 is required for systemic cell-to-cell ROS signaling in response to light stress. A, Arabidopsis plants were subjected to a HL stress treatment applied to a single leaf (Local; indicated with a circle), and ROS accumulation was imaged, using H₂DCFDA, in whole plants (local and systemic tissues). Representative time-lapse images of whole-plant ROS accumulation in WT, hpca1-1 and hpca1-2 plants are shown alongside bar graphs of combined data from all plants used for the analysis at the 0- and 30-min time points (local and systemic). B, Same as in (A), but for whole-plant H₂O₂ accumulation that was imaged using PO1. C, Arabidopsis plants were subjected to a HL stress treatment applied to a single leaf (Local) and the levels of H₂O₂ were measured in extracts from local and systemic leaves using Amplex-Red. All experiments were repeated at least three times with 10 plants of each genotype per experiment. Data are presented as box plot graphs; X is mean ± se, N = 30, *P < 0.05, **P < 0.01, ***P < 0.001, Student t test. Scale bar, 1 cm. See Movie 1 for live imaging.