Involvement of Calyculin A- and Okadaic Acid-sensitive Protein Phosphatase in the Blue Light Response of Stomatal Guard Cells

Calyculin A (CA) and okadaic acid (OA), inhibitors of protein phosphatases, inhibited blue light (BL)-dependent H+pumping in Vicia guard cell protoplasts at half-inhibitory concentrations of 4.5 nM and 400 nM, respectively. Light-induced stomatal opening in Viciaepidermis was completely suppressed by CA at 100 nM and by OA at 1 μM. These results suggest that CA- and OA-sensitive protein phosphatase is involved in the BL response of stomatal guard cells.