Systems Biology of Plant Heterotrimeric G-protein Signaling in Overlapping Pathways Regulating Stomatal Closure

这项研究将研究一种特殊的植物细胞类型对不利环境条件的反应，以提供对活细胞内信号成分如何相互作用以影响细胞功能的新见解。这种特殊的细胞类型，即保卫细胞，出现在表皮中，在那里，一对保卫细胞包裹着被称为气孔的微孔，植物通过气孔吸收二氧化碳(光合作用的底物)，不可避免地失去水分。由此提高对保卫细胞对干旱和大气二氧化碳水平作出反应的调节机制的了解，有助于开发在一系列生长条件下产量更高的作物品种。在这个项目中获得的对生物网络的一般见解将提高对失调细胞信号的理解，对生理学、农业和生物技术具有广泛的影响。包括本科生研究人员在内的人员将在实验生物学和计算生物学的新兴方法方面进行交叉培训。主要研究人员将开发一门新课程，向一年级本科生介绍生物网络和其他数学生物学概念，并鼓励STEM参与。异三聚体G蛋白由G-α亚基和G-β-伽马二聚体组成，构成了一种广泛存在于真菌、动物和植物等生物中的信号机制。这项研究将研究G蛋白在保卫细胞干旱和二氧化碳信号网络中的作用，以解决G-α亚基是否以及如何竞争或划分它们与特定G-β-伽马二聚体的相互作用这一根本问题。在植物中，保卫细胞是最被理解的G蛋白调节的单细胞系统。为了响应激素脱落酸(ABA；干旱和其他逆境的指标)和二氧化碳浓度的升高，保卫细胞中复杂的信号网络被激活，从而驱动气孔关闭。该项目将使用遗传分析来确定在ABA和CO2响应期间，三个拟南芥G-β-伽马二聚体的四个G-ALPA亚基的竞争和分配。这项研究将应用蛋白质-蛋白质相互作用的测试来评估新的候选G蛋白质相互作用因子，并确定G蛋白质信号如何与保卫细胞的其他已知ABA和CO2信号成分相互连接。该项目将开发新的通用可达性分析和组合逻辑方法来描述聚合或重叠的网络，然后将这些方法应用于获得的新实验数据集，以创建G蛋白、ABA和CO2信号的核心组件的新网络模型。开发的用于网络构建的新的组合逻辑方法将促进系统生物学的基本知识：它们将适用于任何生物体的定向信号和遗传网络，并将使范式从假设孤立的线性路径(例如，在经典的上位性分析中)转变为考虑与一组观察相一致的所有网络架构。因此，这项研究的结果将对生物系统中常见但复杂的串扰现象具有普遍意义。

This research will study a specialized plant cell type's response to adverse environmental conditions to provide new insights into how signaling components within living cells interact with each other to affect cell function. This specialized cell type, the guard cell, occurs in the epidermis, where pairs of guard cells enclose microscopic pores called stomata, through which plants take up CO2 (the substrate for photosynthesis) and, inevitably, lose water. Resultant improved understanding of the regulatory mechanisms by which guard cells respond to drought and atmospheric carbon dioxide levels can assist in development of crop varieties with greater yield under a range of growing conditions. General insights into biological networks gained in this project will improve understanding of dysregulated cell signaling, with broad implications for physiology, agriculture, and biotechnology. Personnel, including undergraduate researchers, will be cross-trained in emerging approaches in both experimental and computational biology. The principal investigators will develop a new course to introduce first year undergraduates to biological networks and other mathematical biology concepts and encourage STEM participation. Heterotrimeric G-proteins, composed of G-alpha subunits and G-beta-gamma dimers, comprise a ubiquitous signaling mechanism found in organisms as diverse as fungi, animals, and plants. This research will study G protein involvement in guard cell drought and CO2 signaling networks to address the fundamental question of whether and how G-alpha subunits compete for or partition their interaction with specific G-beta-gamma dimers. In plants, guard cells are the best understood single cell system of G protein regulation. In response to the hormone abscisic acid (ABA; an indicator of drought and other stresses), and to elevated concentrations of CO2, complex signaling networks are activated in guard cells that drive stomatal closure. This project will use genetic analyses to determine competition vs. partitioning of the four G-alpa subunits for the three Arabidopsis G-beta-gamma dimers during ABA and CO2 responses. The research will apply tests of protein-protein interaction to assess new candidate G protein interactors and to determine how G protein signaling interconnects with other known ABA and CO2 signaling components of guard cells. The project will develop new general reachability analysis and combinatorial logic methods to describe convergent or overlapping networks, and these methods will then be applied to the new experimental datasets obtained to create a new network model of the core components of G protein, ABA, and CO2 signaling. The new combinatorial logic methods for network construction developed will advance fundamental knowledge in systems biology: they will be applicable to directional signaling and genetic networks of any organism, and will enable a paradigm shift from assuming isolated linear pathways (e.g. as in classic epistasis analysis) to considering all network architectures consistent with a set of observations. Thus, the results from this research will have general implications for the common but complex phenomenon of cross-talk in biological systems.