Calcium Channel Regulation in Arabidopsis Guard Cells

干旱胁迫是农业生产的主要限制因素。植物失水的95%以上是通过气孔发生的，气孔是由叶表皮中的一对保卫细胞形成的。气孔开闭响应各种环境信号，如光、二氧化碳和水分状况。保卫细胞中的信号网络整合这些信号来调节气孔运动，控制水分损失和二氧化碳吸收。该项目的长期目标是通过研究钙离子通道来剖析这个信号网络，钙离子通道被认为起着关键作用。保卫细胞胞质游离钙浓度升高是脱落酸触发气孔关闭的早期事件。离子通道介导的Ca~(2+)内流引起细胞内Ca~(2+)升高。已有研究表明，过氧化氢可激活保卫细胞质膜上的钙通道。抑制NADPH氧化酶可防止过氧化氢的产生，并减少脱落酸诱导的气孔关闭。此外，初步研究表明，一氧化氮也会触发气孔关闭。本项目将通过细胞生物学、生物物理学和分子遗传学相结合的方法，进一步研究过氧化氢和一氧化氮对钙通道的调节。分析生物活性氧化剂和抗氧化剂对钙离子通道的影响。此外，NADPH氧化酶在保卫细胞脱落酸信号中的作用将被确定。还将研究一氧化氮对气孔运动的影响。在该项目中获得的信息将提供对保卫细胞信号网络的洞察，并有助于识别潜在的分子和遗传目标，用于工程抗旱植物。此外，该项目还可能影响对一氧化氮这一主要空气污染物如何通过植物影响全球生态系统的理解。

Drought stress is a major limitation for agricultural production. More than 95% of water loss from plants occurs via stomatal pores, which are formed by pairs of guard cells in the leaf epidermis. Stomata open and close in response to various environmental signals, such as light, CO2 and water status. A signaling network in guard cells integrates these signals to regulate stomatal movements, which control water loss and CO2 uptake. The long-term goal of the project is to dissect this signaling network by studying Ca2+ channels, which have been proposed to play a key role. Elevation of cytosolic free Ca2+ concentrations in guard cells is an early event during abscisic acid-triggered stomatal closing. Ion channel-mediated Ca2+ influx gives rise to the cytosolic Ca2+ increase. It has been shown previously that hydrogen peroxide activates Ca2+ channels in the plasma membrane of guard cells. Inhibition of NADPH oxidase prevents H2O2 production and reduces abscisic acid-induced stomatal closing. Additionally, preliminary studies have revealed that nitric oxide also triggers stomatal closure. This project will further study H2O2 and nitric oxide regulation of the Ca2+ channels via a combined cell biological, biophysical, and molecular genetic approach. The effects of biologically active oxidants and antioxidants on the Ca2+ channels will be analyzed. Furthermore, the role of NADPH oxidase in guard cell abscisic acid signaling will be determined. The effects of nitric oxide on stomatal movements will also be examined.The information gained in the project will provide insight into the guard cell signaling network and contribute to the identification of potential molecular and genetic targets for engineering drought-resistant plants. Furthermore, the project may also impact on the understanding of how nitric oxide, a major air pollutant, affects the global ecosystem via plants.