Ion Channel Regulation in Higher Plants

高等植物中的离子通道调节

• 批准号: 9506191
• 负责人: Julian Schroeder
• 金额: $ 49.1万
• 依托单位: University of California-San Diego
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-11-01 至 2001-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9506191&HistoricalAwards=false
• 关键词: Ion; Channel; Regulation; Higher; Plants

9506191 Schroeder Stomatal pores in leaves close to reduce transpirational water loss of plants in response to environmental stress conditions such as drought. Control of stomatal movements by guard cells in response to environmental stimuli and stress conditions is a primary factor in determining water use efficiency and productivity of crop plants. Guard cells provide an ideal system to elucidate early events in higher plant signal transduction. Several key guard cell ion channels have been identified which have been proposed to function as important signal transducers and mediators of stomatal closing. Recent data suggest that both Ca2+- dependent and Ca2+-independent transduction cascades may control stomatal closing. However, the intracellular signaling cascades which link signal reception to ion channel modulation during stomatal closing remain largely unknown. Furthermore, the molecular mechanisms have remained unknown, by which guard cell vacuoles release ions, which is essential for stomata closing. The long term goal of this research is to characterize the chain of events of the signaling cascade which integrates physiological stimuli, such as abscisic acid, intracellular coupling proteins, second messengers, and ion channels to produce stomatal closing. To elucidate signaling mechanism in guard cells, we propose studies using a combination of cell biological, patch clamp, biochemical and genetic analyses. Recent research has led to the model that slow anion channels and outward-recitifying K+ channels in the plasma membrane and newly identified vacuolar K+ (VK) and Ca2+- activated Ca2+-permeable (SV) channels in the tonoplast of guard cells are central transducers and mediators of stimulus-dependent stomatal closing. The regulation and roles of the newly identified VK channels and the proposed Ca2+-induced Ca2+ release by SV channels in guard cell vacuoles will be investigated in detail to test the hypothesis that these vacuolar ion chan nels are crucial for signal transduction and vacuolar ion release during stomatal closure. Furthermore, studies of these vacuolar ion channels together with analyses of rate-limiting slow anion channels in guard cell plasma membrane will be pursued to determine intermediate Ca2+-dependent and putative Ca2+- independent signaling steps which produce the integrated response of stomatal closing. Regulation of guard cell vacuole channels and phosphorylation-dependent plasma membrane slow anion channels will further be studied by using isoforms of the Ca2+-dependent protein kinase (CDPK). In addition, cell biological characterization of guard cell signaling mutants in Arabidopsis will be pursued to elucidate the function of genetic loci within the cascade of events which produced stomatal closing. Stomatal regulation ion abscisic acid-insensitive Arabidopsis mutants (abi1 and abi2) and effects of the purified recombinant ABI1 protein phsophatase on guard cell ion channels will be pursued for enhanced ABA sensitivity and for phenotypic stomatal responses in existing Arabidopsis mutants to identify and characterize additional genetic loci involved in stomatal and ABA signaling. The proposed research will contribute significantly to the understanding of the molecular mechanisms of the signal transduction cascade which produces the integrated response of stomatal closing. These studies may further provide important information for the design of strategies for future engineering of improved water use efficiency in crop plants. %%% Plants "breathe" through tiny openings or "mouths" called stomata which are often found on the underside of leaves. However, a fine balance must be achieved between respiration and loss of water vapor through the stomata. To achieve this balance, the plant is sensitive to a wide variety of environmental stimuli which induce stomatal closure, such as elevated carbon dioxide levels, darkness and the phytohormone abscisic acid (ABA). It is known that stomatal closing is, in part, brought about by ion efflux through ion channels in the outer cell membrane and the membrane which surrounds the vacuole, the tonoplast of the cells which comprise the stomate, the guard cells. This project is concerned with the way the environment stimuli bring about changes in the amount and rate of ion transport through these channels. The channels have been identified. Potassium is released from the vacuole through the tonoplast, into the cytoplasm where it is released into the cell wall via an outward-rectified potassium channel. A rise in intracellular calcium and pH stimulates this release. The regulation and role of the newly-identified vacuolar potassium transporter is explored, as is the coordination of these channels with others at the plasma membrane to produce an integrated response to intracellular calcium signals. The integration of the signaling pathways is also explored using molecular genetics. Mutants which have the phenotype of an altered guard cell response to the phytohormone, ABA, are analyzed in order to identify more genes involved in stomatal opening and ABA signaling. The role of one of these signaling genes, one which encodes a protein phosphatase, is being explored by purifying the protein and determining its direct effect on channel physiology. This project has biotechnical application through the design of crop plants which have improved water use efficiency. ***

9506191 Schroeder 叶子中的气孔关闭，以减少植物因干旱等环境胁迫条件而蒸腾失水。 保卫细胞响应环境刺激和胁迫条件而控制气孔运动是决定作物水分利用效率和生产力的主要因素。 保卫细胞提供了一个理想的系统来阐明高等植物信号转导的早期事件。 已经确定了几个关键的保卫细胞离子通道，它们被认为充当重要的信号传感器和气孔关闭的介质。 最近的数据表明，Ca2+依赖性和Ca2+非依赖性转导级联都可以控制气孔关闭。 然而，在气孔关闭期间将信号接收与离子通道调制联系起来的细胞内信号级联仍然很大程度上未知。 此外，保卫细胞液泡释放离子的分子机制仍然未知，而离子对于气孔关闭至关重要。 这项研究的长期目标是表征信号级联的事件链，该信号级联整合了生理刺激，例如脱落酸、细胞内偶联蛋白、第二信使和离子通道以产生气孔关闭。 为了阐明保卫细胞中的信号传导机制，我们建议结合细胞生物学、膜片钳、生化和遗传分析进行研究。 最近的研究得出了这样的模型：质膜中的慢阴离子通道和外向重传 K+ 通道以及保卫细胞液泡膜中新发现的液泡 K+ (VK) 和 Ca2+ 激活的 Ca2+ 通透性 (SV) 通道是刺激依赖性气孔关闭的中心换能器和介质。 将详细研究新发现的 VK 通道的调节和作用以及保卫细胞液泡中 SV 通道所提出的 Ca2+ 诱导的 Ca2+ 释放，以检验这些液泡离子通道对于气孔关闭期间的信号转导和液泡离子释放至关重要的假设。 此外，对这些液泡离子通道的研究以及对保卫细胞质膜中限速慢阴离子通道的分析将被继续进行，以确定产生气孔关闭的综合反应的中间Ca2+依赖性和假定的Ca2+非依赖性信号传导步骤。 将通过使用 Ca2+ 依赖性蛋白激酶 (CDPK) 的亚型进一步研究保卫细胞液泡通道和磷酸化依赖性质膜慢阴离子通道的调节。 此外，将研究拟南芥中保卫细胞信号传导突变体的细胞生物学特征，以阐明产生气孔关闭的级联事件中遗传位点的功能。 将研究对脱落酸不敏感的拟南芥突变体（abi1 和 abi2）的气孔调节离子以及纯化的重组 ABI1 蛋白磷酸酶对保卫细胞离子通道的影响，以增强现有拟南芥突变体的 ABA 敏感性和表型气孔反应，以鉴定和表征参与气孔和 ABA 信号传导的其他遗传位点。 拟议的研究将极大地有助于理解信号转导级联的分子机制，该级联产生气孔关闭的综合反应。 这些研究可能进一步为未来提高作物水分利用效率的工程设计策略提供重要信息。 %%% 植物通过称为气孔的微小开口或“嘴”进行“呼吸”，气孔通常位于叶子的背面。 然而，呼吸和通过气孔的水蒸气损失之间必须实现良好的平衡。为了实现这种平衡，植物对多种导致气孔关闭的环境刺激敏感，例如二氧化碳水平升高、黑暗和植物激素脱落酸 (ABA)。 已知气孔关闭部分是由通过外细胞膜和围绕液泡的膜、包含气孔的细胞的液泡膜、保卫细胞中的离子通道的离子流出引起的。该项目关注环境刺激如何导致通过这些通道的离子传输量和速率发生变化。 渠道已经确定。 钾通过液泡膜从液泡释放到细胞质中，并通过向外整流的钾通道释放到细胞壁中。 细胞内钙和 pH 值的升高会刺激这种释放。 探索了新发现的液泡钾转运蛋白的调节和作用，以及这些通道与质膜上其他通道的协调，以产生对细胞内钙信号的综合反应。 还利用分子遗传学探索信号通路的整合。 对具有改变的保卫细胞对植物激素 ABA 反应的表型的突变体进行分析，以鉴定更多参与气孔开放和 ABA 信号传导的基因。这些信号基因之一（编码蛋白磷酸酶的基因）的作用正在通过纯化蛋白质并确定其对通道生理学的直接影响来探索。 该项目通过作物植物的设计进行生物技术应用，提高了水的利用效率。 ***