Figure 1: Chloroplast Ca²⁺ dynamics.

(a–f,h) Aequorin (AEQ) luminescence from wild-type (WT) AEQ-expressing plants treated with (a) 1 μM flg22, (b) 100 μg ml⁻¹ chitin, (c) light-to-dark transition, (d) ice-cold MS medium, (e) 200 mM NaCl, (f) 500 mM sorbitol or (h) 30 μM ionomycin. The vertical dashed line indicates the time at which treatment was initiated. Experiments were repeated at least five times, with control treatments. Representative data are shown. Cytosolic and stromal Ca²⁺ changes are indicated by grey and black lines, respectively. (g) Effects of signal transduction inhibitors on flg22-induced cytosolic and stromal Ca²⁺ increase in WT AEQ-expressing plants. '−': no inhibitor, BPT: 5 mM 1,2-bis(2-aminophenoxy)ethane N,N,N′,N′-tetraacetic acid (BAPTA), K: 2 μM K252a, U: 20 μM U-0126, DPI: 50 μM DPI. The time-integrated cytosolic or stromal Ca²⁺ concentration upon 30-min treatment with 1 μM flg22 is shown. Data are the means±s.e.m. of relative values (n=4, control values were set of 100%). (i,j) Stromal Ca²⁺ changes in WT (black lines, white bars) and cas-1 knockout (red lines and bars) plants expressing AEQ. Plants were treated with (i) 1 μM flg22 or (j) light-to-dark transition. The integrated stromal Ca²⁺ concentration was reduced in cas-1 compared with WT. Data are the means±s.e.m. of relative values (n=4).