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

了解控制极化植物细胞生长的基本机制是生物学中一个重要的悬而未决的问题，对于具有改善生长特性的植物的未来发展至关重要。极化植物细胞生长是一种高度集中的生长类型，对陆地定居、有性繁殖、水分和养分吸收至关重要。肌动蛋白细胞骨架是调控极化细胞生长的核心分子，它是一种进化保守的动态纳米聚合物(肌动蛋白细丝)和纳米马达(肌球蛋白)的组装。已知肌动蛋白细胞骨架参与细胞内成分的组织，包括内膜和含有对细胞生长重要的物质的分泌小泡。这项研究的长期目标是了解肌动蛋白细胞骨架和内膜间隔如何相互作用，以产生两极分化的植物细胞生长。为了实现这一目标，该项目的目标是确定运动肌球蛋白XI在肌动蛋白细丝、内膜和生长物质的极化分泌之间的协调作用。中心假设是膜室，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的运输合作产生极化分泌。以下三个特定的目的是为了验证这一中心假说：1)确定与肌球蛋白XI相关的膜室；2)确定将肌球蛋白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，肌球蛋白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。该项目将研究一种新的极化分泌机制，该机制基于肌球蛋白XI和肌动蛋白聚合的协同作用，使用独特的基因工具来降低肌球蛋白XI的整体活性或仅降低其货物结合活性。这项研究为细胞极化提供了一个可行的模型，该模型由膜内隔室、肌球蛋白XI和动态肌动蛋白细胞骨架的协同作用驱动。更广泛的影响。除了有助于对生物学的基本了解外，从这个项目中获得的知识还有可能确定改善植物繁殖、植物适合性和植物生长的策略。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，该项目对迅速发展的生物学领域产生了影响，该领域对显微镜和成像教育和培训的需求越来越大。为了将这些学科整合到普通生物学课程中，将实施一门新的显微镜和成像课程。实验室和探究式课程的目标是训练学生在课堂上和作为独立研究项目的一部分在研究中应用显微镜。新课程将采用模块化形式，允许将部分课程用于外展计划。该项目还通过继续为博士后学者开发一个社交网络工具(LectureBank.org)，重点是未被充分代表的少数族裔生命科学家，提供了在博士后经历期间改进陈述和网络技能的机会。该工具作为一个点对点的指导资源，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.