CAREER: Role of Plant Myosin XI in Polarized Secretion and Actin Dynamics

了解植物细胞极化生长的基本机制是生物学中尚未解决的一个重要问题，这对未来植物生长特性的改善至关重要。极化植物细胞生长是一种高度集中的生长类型，对陆地定植、有性繁殖、水和营养吸收至关重要。在细胞极化生长的调控中，肌动蛋白细胞骨架是一个核心角色，它是一种进化上保守的动态纳米聚合物（肌动蛋白丝）和纳米马达（肌球蛋白）的组合。已知肌动蛋白细胞骨架参与细胞内成分的组织，包括细胞内膜和含有细胞生长重要物质的分泌囊泡。该研究的长期目标是了解肌动蛋白细胞骨架和内膜室如何相互作用以产生极化植物细胞生长。为了实现这一目标，该项目的目的是确定运动肌球蛋白XI在肌动蛋白丝、膜和生长物质极化分泌之间的协调中的作用。核心假设是膜室，如分泌囊泡，作为活跃的组织中心，在那里肌动蛋白聚合和基于肌球蛋白xi的运输协同产生极化分泌。以下三个具体目标旨在以苔藓小立藓作为植物模型系统来验证中心假设：1)确定与肌球蛋白XI相关的膜室；2)鉴定将肌球蛋白XI固定在其膜货物上的受体；3)确定在极化细胞生长过程中，肌凝蛋白XI、肌动蛋白聚合和内膜如何协同调节肌动蛋白细胞骨架的组织。该项目将研究一种基于肌凝蛋白XI和肌动蛋白聚合合作的极化分泌新机制，使用独特的遗传工具来降低肌凝蛋白XI的整体活性或仅其货物结合活性。该研究提供了一种可行的细胞极化模型，该模型是由内膜室、肌凝蛋白XI和动态肌动蛋白细胞骨架共同作用驱动的。更广泛的影响。除了有助于对生物学的基本理解之外，从该项目中获得的知识还具有确定改善植物繁殖，植物适应性和植物生长的策略的潜力。这些改进可以通过促进具有更可持续未来所需特征的植物的发展来影响农业科学。从教育的角度来看，该项目影响了快速发展的生物学领域，该领域对显微镜和成像教育和培训的需求日益增加。为了将这些学科整合到普通生物学课程中，我们将开设一门新的显微镜和成像课程。这门以实验和探究为基础的课程的目标是训练学生在课堂上和独立研究项目中应用显微镜进行研究。新课程将采用模块化的形式，允许将其中的一些部分用于拓展项目。该项目还为博士后学者提供了机会，通过继续开发一个社会网络工具（LectureBank.org），提高博士后期间的演讲和网络技能，重点关注被忽视的少数民族生命科学家。该工具作为点对点的指导资源，并提供了一个分享材料和经验的论坛。

Understanding the fundamental mechanisms that govern polarized plant cell growth is an important unsolved problem in biology that is critical for future development of plants with improved growth characteristics. Polarized plant cell growth is a highly focused type of growth essential for land colonization, sexual reproduction, and water and nutrient uptake. A central player in the regulation of polarized cell growth is the actin cytoskeleton, an evolutionarily conserved assembly of dynamic nano-polymers (actin filaments) and nano-motors (myosins). The actin cytoskeleton is known to participate in the organization of components inside the cell, including endomembranes and secretory vesicles containing materials important for cell growth. The long-term goal of the research is to understand how the actin cytoskeleton and endomembrane compartments interact to generate polarized plant cell growth. Toward accomplishing this goal, the objective of the project is to determine the role of the motor myosin XI in the coordination between actin filaments, endomembranes, and polarized secretion of growth materials. The central hypothesis is that membrane compartments, such as secretory vesicles, function as active centers of organization where actin polymerization and myosin XI-based transport cooperate to produce polarized secretion. The following three specific aims are designed to test the central hypothesis using the moss Physcomitrella patens as a plant model system: 1) identify the membrane compartments associated with myosin XI; 2) identify the receptors that anchor myosin XI to its membrane cargo; and 3) determine how myosin XI, actin polymerization, and endomembranes cooperate to regulate the organization of the actin cytoskeleton during polarized cell growth. The project will investigate a novel mechanism for polarized secretion based on the cooperation of myosin XI and actin polymerization using unique genetic tools developed to reduce overall myosin XI activity or only its cargo binding activity. The research provides a viable model for cell polarization driven by the concerted action of endomembrane compartments, myosin XI, and a dynamic actin cytoskeleton. Broader Impacts. In addition to contributing to the basic understanding of biology, the knowledge obtained from this project has the potential to identify strategies to improve plant reproduction, plant fitness, and plant growth. These improvements can impact agricultural science by promoting the development of plants with characteristics necessary for a more sustainable future. From an educational perspective, the project impacts the rapidly advancing field of biology where there is an increasing need for microscopy and imaging education and training. In order to integrate these disciplines within the general biology curriculum, a new microscopy and imaging course will be implemented. The goal of the laboratory and inquiry-based course is to train students to apply microscopy in research both in class and as part of independent research projects. The new course will have a modular format that allows the use of some of its parts for outreach programs. The project also provides opportunities for improving presentation and networking skills during the postdoctoral experience through the continued development of a social networking tool (LectureBank.org) for postdoctoral scholars with an emphasis on underrepresented minority life scientists. The tool serves as a peer-to-peer mentoring resource and provides a forum for sharing materials and experiences.