%0 Journal Article
%T Dual Role of Hydrogen Peroxide in Arabidopsis Guard Cells in Response to Sulfur Dioxide
%A Huilan Yi
%A Xin Liu
%A Min Yi
%A Gang Chen
%J Advances in Toxicology
%D 2014
%R 10.1155/2014/407368
%X Sulfur dioxide (SO2) is a major air pollutant and has significant impacts on plant physiology. Plant can adapt to SO2 stress by controlling stomatal movement, gene expression, and metabolic changes. Here we show clear evidences that SO2-triggered hydrogen peroxide (H2O2) production mediated stomatal closure and cell death in Arabidopsis leaves. High levels of SO2 caused irreversible stomatal closure and decline in guard cell viability, but low levels of SO2 caused reversible stomatal closure. Exogenous antioxidants ascorbic acid (AsA) and catalase (CAT) or Ca2+ antagonists EGTA and LaCl3 blocked SO2-induced stomatal closure and decline in viability. AsA and CAT also blocked SO2-induced H2O2 and elevation. However, EGTA and LaCl3 inhibited SO2-induced increase but did not suppress SO2-induced H2O2 elevation. These results indicate that H2O2 elevation triggered stomatal closure and cell death via signaling in SO2-stimulated Arabidopsis guard cells. NADPH oxidase inhibitor DPI blocked SO2-induced cell death but not the stomatal closure triggered by low levels of SO2, indicating that NADPH oxidase-dependent H2O2 production plays critical role in SO2 toxicity but is not necessary for SO2-induced stomatal closure. Our results suggest that H2O2 production and accumulation in SO2-stimulated plants trigger plant adaptation and toxicity via reactive oxygen species mediating Ca2+ signaling. 1. Introduction Sulfur dioxide (SO2) is a harmful gas that is emitted largely from burning coal, high-sulfur oil, and fuels. During the past few decades, the concentration of SO2 in the atmosphere has increased in many areas of the world, especially in the developing countries. High levels of SO2 can injure many plant species and varieties, resulting in photosynthesis decline, growth inhibition, and even death [1¨C4]. Sulfur dioxide enters plants mainly through the open stomata [5]. Once it enters the leaf, SO2 is hydrated to form and . The toxicity of SO2 is derived from molecular species sulfite () and bisulfite () generated after SO2 is dissolved in cellular fluid [6]. Sulfite oxidation, which is the detoxification reaction of sulfite to sulfate (), leads to the formation of reactive oxygen species (ROS) in plant cells [7, 8]. The production and accumulation of ROS are one of the key events in plant response to SO2 [9¨C12]. ROS have been proposed as central components of plant response to both biotic and abiotic stresses. Under such conditions, ROS may play two very different roles: exacerbating damage or signaling the activation of defense responses [13, 14]. It has been
%U http://www.hindawi.com/journals/atox/2014/407368/