Role of Cytoplasmic Alkalization and Nitric Oxide in Ethylene-induced Stomatal Closure in Arabidopsis

Ethylene-induced stomatal closure is well-known. However, the mechanism by which ethylene closes stomata remains clear. This research was conducted to explore the roles of guard cell cytoplasmic alkalization and nitric oxide (NO) and the relationship between them during stomatal closure by ethylene. To achieve this goal, we used pharmacological approach, confocal laser scanning microscope and Arabidopsis mutant etr1-1 and etr1-3, which have defect in ethylene perception and Nia2-1, Nia1-2 and Nia1-2/Nia2-5, which are NO generation enzyme nitrate reductase (NR) mutant. Our data show that ethylene precursor ACC induced stomatal closure by promoting guard cell cytoplasmic alkalization and subsequent NO synthesis. ACC caused the rises in cytosol pH and NO level and promoted stomatal closing in the wild type but did not in mutant etr1-1 and etr1-3. Furthermore, ACC failed to induce guard cells cytosol alkalization in the wild type in the presence of butyric acid and NO generation in Nia1-2 and Nia1-2/Nia2-5, which is coincide with its effects on stomatal aperture in these plants. Cytosol alkalization and Nia1-dependent NO generation were vital for ethylene-led reduction of stomatal aperture. Moreover, the rise in cytosol pH was prerequisite for NO production by ethylene. Butyric acid prevented ACC-triggered NO synthesis in the wild type but ACC enhanced cytosol pH in Nia1-2 and Nia1-2/Nia2-5. SNP rescued the defect of ACC-led stomata closing in the wild type in the presence of butyric acid but methylamine did not reverse the impairment of ACC-led stomata closing in Nia1-2 and Nia1-2/Nia2-5. Taken together, the present study unambiguously reveals that ethylene induces guard cell cytosol alkalization, and then promotes Nia1-dependent NO synthesis and finally initiates stomata closing in Arabidopsis. (C) 2017 Friends Science Publishers