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 Vicia epidermis was completely suppressed by CA at 100 nM and by OA at 1 mu M. These results suggest that CA- and OA-sensitive protein phosphatase is involved in the BL response of stomatal guard cells.