Fig. 5.

CO₂ concentration does not affect the OST1/SnRK2 protein kinase activity in guard cells. (A and B) In-gel kinase assays show OST1/SnRK2 kinase activity in guard cells. Col-0 (WT) or ost1-3 mutant guard cell protoplasts were incubated in CO₂-equilibrated buffer (150 or 900 ppm CO₂), 10 μM ABA or 13.5 mM NaHCO₃ as indicated for 30 min at room temperature; 0.25% EtOH and 27 mM sorbitol were used as controls for ABA and NaHCO₃ treatments, respectively. (B) Phosphor screen was exposed for 3 d to in-gel kinase gel enabling visualization of basal protein kinase activities at ∼42–45 kDa. CBB staining is shown as a loading control. The presented data are representative results of five independent experiments (see also SI Appendix, Fig. S9).