Induction of stomatal closure by vanadate or a light/dark transition involves Ca2+-calmodulin-dependent protein phosphorylations

Abstract

Previous studies indicate that a continual source of adenosine 5′-triphosphate is required for both opening and closing of stomata. However, vanadate (Na3VO4 at 500 μM) as well as a light/dark transition induced stomatal closing in epidermal peels of Commelina commuais L., showing that the stoppage or even the decrease of the activity of the plasma membrane H+-adenosine 5′-triphosphatase is sufficient to induce stomatal closure. Furthermore, stomatal closing in response to Na3VO4 or a light/ dark transition was suppressed by inhibitors of metabolism (10 μM carbonyl cyanide m-chlorophenylhydrazone) and of protein kinases (20 μM 1-[5-iodonaphthalene-1-sulfonyl]-1H-hexa-hydro-1,4-diazepine), calmodulin antagonists (20 μM N-[6-aminohexyl]-5-chloro-1-naphthalenesulfonamide), and the anion channel blocker 5-nitro-2,3-phenylpropyllamino benzoic acid (50 μM). These data suggest that the slow, outward rectifying anion channel, whose opening would be related to the membrane potential, and at least one step requiring a protein phosphorylation by a Ca2+-calmodulin-dependent protein kinase of the myosin light chain kinase type might be implicated in the induction of stomatal closing by vanadate or a light/dark transition.