Figure 1.

CPK3 kinase activities and salt-sensitive phenotype of cpk3 mutants.(a) Activation of transiently expressed HA-epitope tagged CPK3 in response to different stresses in Arabidopsis protoplasts. Immunocomplex kinase assays were performed as described in Experimental procedures. The top panel shows the incorporation of ³²P into the generic substrate Histone IIIS, and the bottom panel displays CPK3 protein levels: 0, mock treatment; cold, 4°C; NaCl, 150 mm; heat, 37°C; H₂O₂, 1 mm; flagellin, 15 nm; laminarin, 1 mm.(b) Endogenous CPK3 kinase activity in response to salt stress in roots of cpk3-2 knock-out and Col-0 plants measured in immunocomplex kinase assays. Plants were treated with 150 mm NaCl for 0, 10 and 30 min. Immunocomplex kinase assays were performed in the absence or presence 200 μm EGTA.(c) CPK3 transcript levels in response to salt stress.(d) CPK3 protein levels in Col-0 and three independent T-DNA insertion lines.(e) Germination rates of Col-0 and the T-DNA insertion lines on quarter-strength Hoagland + 150 mm NaCl. Error bars indicate SEM (n = 10). Statistically significant differences from Col-0 calculated by a two-tailed Student’s t-tests: *P ≤ 0.05; **P ≤ 0.001.