Copper amine oxidase-catalysed hydrogen peroxide involves production of nitric oxide in darkness-induced stomatal closure in broad bean

Abstract

Hydrogen peroxide is an important intermediate in darkness-induced stomatal closure. In the present work, we provide evidence that copper amine oxidase (CuAO) was involved in H2O2 production in darkness-induced stomatal closure in Vicia faba L. Darkness activated CuAO in intercellular washing fluid from leaves. Aminoguanidine (AG) and 2-bromoethylamine (BEA), which were both irreversible inhibitors of CuAO, significantly suppressed darkness-induced stomatal closure and H2O2 generation. The effects of AG and BEA were reversed only by H2O2 but not by other products of CuAO. These results indicate that CuAO participates in darkness-induced stomatal closure through its reaction product, H2O2. Furthermore, darkness-induced nitric oxide (NO) production and cytosolic alkalinisation were obviously inhibited by AG and BEA, and only H2O2, among the products of CuAO, could reverse the effects, implying that the CuAO-catalysed product H2O2 is required for NO production and cytosolic alkalinisation to a large extent in darkness-induced stomatal closure. In addition, butyric acid blocked but methylamine enhanced the ability of H2O2 to reverse the effect of BEA on NO production, suggesting that cytosolic alkalinisation is involved in CuAO-mediated NO generation in darkness-induced stomatal closure.