Calcium Dependent Protein Kinases in Pollen Tube Tip Growth

这个项目的长期目标是了解钙依赖蛋白激酶(CPK)在调节植物生长发育的许多方面的功能。CPK(由一种新的结构定义，在这种结构中，激酶结构域与钙调素样调制域融合在一起)似乎是植物和某些单细胞生物体所特有的，在动物中没有发现。在模式植物拟南芥中，有34个CPK，其中12个在花粉中表达。虽然许多植物CPK被认为参与调节对干旱、高温和寒冷等环境胁迫的反应，但最近获得的遗传证据表明，其中两个CPK对花粉管顶端的生长至关重要，这是一种发育程序。CPK17和34的基因敲除导致1)花粉管短而生长缓慢，并破坏了它们定位和受精胚珠的能力；2)产生了基本上不育的植物。通过将CPK34基因转移到这些植物中恢复正常生育能力的能力为确定CPK对其功能重要的特征提供了前所未有的机会。指导这项研究的一个关键假设是，CPK17和34的特定功能是在激活域中编码的。该项目的目标包括1)确定这些CPK促进花粉管顶端生长和定向的分子途径，2)描述这些CPK调控的细胞过程，从生长中的花粉管顶端的内吞和胞吐开始，以及3)确定这些CPK如何调节囊泡运输和细胞骨架动力学，这是极化花粉顶端生长的关键过程。这项研究将为植物系统中钙信号的编码和解码提供新的见解。更广泛的影响。这项研究将产生来自教育和指导贡献的额外影响。哈珀实验室积极参与所有学术水平的指导研究活动，从早期职业助理教授到本科生。计划中的研究将在分子生物学、共聚焦显微镜、遗传学和蛋白质组学领域为本科生和研究生提供培训。项目成果将通过出版物、数据库贡献、科学研讨会和面向本科生和K-12学生的讲座向公众传播。

The long-term goal of this project is to understand the functions of calcium-dependent protein kinases (CPKs) in regulating many aspects of plant growth and development. CPKs (which are defined by a novel structure in which the kinase domain is fused to a calmodulin-like regulatory domain) appear to be unique to plants and certain single-celled organisms, and have not been found in animals. In the model plant Arabidopsis, there are 34 CPKs, 12 of which are expressed in pollen. While many plant CPKs are thought to be involved in regulating the response to environmental stresses, such as drought, heat and cold, recent genetic evidence has been obtained that identifies two of these CPKs as critical to pollen tube tip growth, which is a developmental program. Genetic knockout of CPK17 and 34 results 1) in pollen tubes that are short and slow growing and that are disrupted in their ability to locate and fertilize ovules, and 2) in plants that are essentially sterile. The ability to restore normal fertility by transferring CPK34 genes into these plants provides an unprecedented opportunity to determine the features of a CPK that are important for their functions. A key hypothesis guiding the research is that specific functions of CPK17 and 34 are encoded in the kinase domain. The aims of this project include 1) defining the molecular pathways by which these CPKs promote pollen tube tip growth and tropism, 2) delineating the cellular processes regulated by these CPKs, starting with endocytosis and exocytosis at the tip of a growing pollen tube, and 3) identifying how these CPKs regulate vesicle trafficking and cytoskeletal dynamics, which are critical processes in polarized pollen tip growth. This research will provide new insights into how calcium signals are coded and decoded in plant systems. Broader impacts. The research will have additional impacts that derive from educational and mentoring contributions. The Harper lab is actively engaged in mentoring research activities at all academic levels, from early career assistant professors to undergraduates. The planned research will provide training for both undergraduate and graduate student in the area of molecular biology, confocal microscopy, genetics and proteomics. Project results will be communicated to the public through publications, data base contributions, scientific seminars, and lectures to undergraduates and K-12 students.