Stress Hormone Signal Transduction in Arabidopsis

描述（由申请人提供）：脱落酸是植物中的一种中枢应激激素，其介导快速细胞反应，下调细胞增殖，引起细胞周期停滞并抑制生长。下调细胞增殖的信号转导机制对于控制有丝分裂至关重要。脱落酸（阿坝）信号转导将在拟南芥保卫细胞中进行研究，拟南芥保卫细胞已经发展成为一个强大的分子遗传学、基因组学和时间分辨的信号系统，用于定量解剖在早期信号级联中介导特异性的复杂分子机制。我们将分析一个新发现的主要早期阿坝信号转导途径的细胞机制。简而言之，我们发现阿坝导致保卫细胞中活性氧（ROS）的快速产生，这反过来又激活质膜钙（Ca 2+）通道。这产生了阿坝信号转导所需的Ca 2+振荡参数的定义窗口。我们鉴定了在新识别的ABA-ROS-Ca 2+中的不同点起作用的阿坝信号转导突变体。振荡信号通路，包括NADPH氧化酶基因AtrbohD &F、PP 2C磷酸酶和mRNA帽结合蛋白ABH 1中的突变。 我们将测试假设：阿坝生物化学激活膜NADPH氧化酶，导致ROS产生;负调节Ca 2+传感器在阅读特异性Ca 2+振荡中起作用;以及abh 1由于早期阿坝信号转导子的mRNA加工而放大ABA诱导的Ca 2+振荡。为了解决这些假设，我们将追求以下具体目标：（1）表征介导快速ABA诱导的ROS产生的生化和分子机制，并表征与abi 1 -1 PP 2C复合的蛋白质。(2)分析ROS激活Ca 2+通道的机制并分离Ca 2+通道基因。(3)真核生物中负责阅读特定钙振荡的机制在很大程度上仍然未知。描述TCH 2和CalcineurinB-AtCBL Ca 2+感觉蛋白在阅读Ca 2+振荡中的作用。(4)表征abh 1 mRNA帽结合突变体放大ABA诱导的Ca 2+振荡的机制。一个新的病毒诱导的基因沉默为基础的筛选将寻求确定新的冗余阿坝信号突变体。这些研究将揭示一个新认识的早期信号通路控制阿坝胁迫信号转导的重要的基本机制，并将有助于对真核生物中Ca 2+信号特异性的全面了解。

DESCRIPTION (provided by applicant): Abscisic acid is a central stress hormone in plants which mediates rapid cellular responses, down regulates cell proliferation, causes cell cycle arrest and inhibits growth. Signal transduction mechanisms that down regulate cell proliferation are of central importance for controlling mitogenesis. Abscisic acid (ABA) signal transduction will be investigated in Arabidopsis guard cells, which have been developed as a powerful molecular genetic, genomic and time-resolved signaling system for quantitatively dissecting the complex molecular machinery mediating specificity in early signaling cascades. We will analyze the cellular mechanisms of a newly revealed major early ABA signal transduction pathway. In brief, we showed that ABA causes rapid production of reactive oxygen species (ROS) in guard cells, which in turn activate plasma membrane calcium (Ca2+) channels. This produces a defined window of Ca2+ oscillation parameters that are required for ABA signal transduction. We identified ABA signaling mutants that function at distinct points in the newly recognized ABA-ROS-Ca2+. oscillation signaling pathway, including mutations in the NADPH oxidase genes AtrbohD &F, PP2C phosphatases and the mRNA cap binding protein ABH1. We will test the hypotheses: that ABA biochemically activates membrane NADPH oxidases causing ROS production; that negatively regulating Ca2+ sensors function in reading specific Ca2+ oscillations; and that abh1 amplifies ABA-induced Ca2+ oscillations due to mRNA processing of early ABA signal transducers. To address these hypotheses, we will pursue the following specific aims: (1) Characterize biochemical and molecular mechanisms mediating rapid ABA-induced ROS production and characterize proteins complexed with the abi1-1 PP2C. (2) Analyze mechanisms by which ROS activate Ca2+ channels and isolate the Ca2+ channel genes. (3) The mechanisms responsible for reading specific calcium oscillations remain largely unknown in eukaryotes. Characterize the roles of the TCH2 and CalcineurinB-AtCBL Ca2+ sensory proteins in reading Ca2+ oscillations. (4) Characterize the mechanisms by which the abh1 mRNA cap binding mutant amplifies ABA-induced Ca2+ oscillations. A new virus-induced gene silencing-based screen will be pursued for identifying novel redundant ABA signaling mutants. These studies will reveal important fundamental mechanisms by which a newly recognized early signaling pathway controls ABA stress signal transduction and will contribute to a general understanding of Ca2+ signaling specificity in eukaryotes.