COLLABORATIVE: Functional Analysis of Arabidopsis Formins, a Family of Actin-Nucleating Proteins

智力优势：肌动蛋白微丝是所有真核生物中至关重要的细胞骨架结构。肌动蛋白微丝形成的限速步骤是前两到三个肌动蛋白单体分子的聚合，称为肌动蛋白成核。formmins是两个已知的肌动蛋白成核蛋白家族之一。植物形成蛋白在肌动蛋白成核活性域与其他生物的同类蛋白有相似之处，但它们中的大部分（称为I类植物形成蛋白）具有植物特有的特征，即具有潜在的糖基化的细胞外结构域和跨膜结构域，将细胞质肌动蛋白成核结构域锚定在细胞表面。本项目旨在确定拟南芥中3个I族形成蛋白，花粉特异性AFH3，花粉、胚乳和营养细胞表达AFH5，以及根分生组织表达AFH6在植物生长发育中的功能作用。作为I组形成蛋白，这些afh作为直接介导肌动蛋白细胞骨架的细胞外刺激的完美候选者，其功能类似于动物细胞整合素的功能。Drs。张，Wu和Kieliszewski计划通过结合遗传和细胞生物学分析来阐明这些I类AFHs在植物生长发育中的功能作用。我们将研究选定的I组胞外结构域的糖基化特性，以及这三种AFHs（以及AFH1，一种典型的、迄今为止最具特征的植物双胍）胞外结构域的功能意义。张博士和她的同事们也将开始努力识别与AFH3和AFH5相互作用的蛋白质，这将导致阐明这些植物形成蛋白的调节和功能的蛋白质网络。更广泛的影响：在资源开发方面，张博士和她的同事将为社区提供构建物、种子和抗体。pi通常在其实验室中接待和培训博士后、研究生和本科生，并计划在本项目的背景下继续这样做。自1997年以来，张博士已经指导了大约40名本科生，其中包括一些来自未被代表的种族群体，目前有本科生参与与该项目相关的持续努力。Kieliszewski博士也一直在她的实验室里指导本科生。这些本科生中有许多人继续攻读科学研究生院。除了pi本身，张和Kieliszewski实验室的博士后和高级研究生都对本科生的直接培养做出了贡献，从而为他们未来的职业发展提供了指导和教学经验。总的来说，这个研究项目将为本科生、研究生和博士后提供广泛的、不同层次的培训领域。

Intellectual Merit: Actin microfilaments are critical cytoskeletal structures in all eukaryotes. The rate-limiting step in the formation of actin microfilaments is the polymerization of the first two to three monomeric actin protein molecules, known as actin nucleation. Formins are one of two known families of actin-nucleating proteins. Plant formins share similarity with their counterparts from other organisms in their actin-nucleating activity domain, but a large number of them (referred to as Group I plant formins) have the plant-unique feature of having a potentially glycosylated extracellular domain and a transmembrane domain that anchor the cytosolic actin-nucleating domain to the cell surface. This project aims to determine the functional roles of 3 group I formins from Arabidopsis, the pollen-specific AFH3, the pollen-, endosperm- and vegetative cell-expressed AFH5, and the root meristem-expressed AFH6, in plant growth and development. As group I formins, these AFHs serve as perfect candidates for mediating extracellular stimuli directly to the actin cytoskeleton, in a manner analogous to the function of integrins of animal cells. Drs. Cheung, Wu and Kieliszewski plan to elucidate the functional roles for these Group I AFHs in plant growth and development through a combination of genetic and cell biological analyses. The glycosylation properties of selected group I extracellular domains and the functional significance of the extracellular domains for these three AFHs (and that of AFH1, a prototypical and thus far the best-characterized plant formin) will be examined. Dr. Cheung and her colleagues will also begin efforts to identify proteins that interact with AFH3 and AFH5, which should lead to elucidation of the protein networks that underlie the regulation and functions of these plant formins. Broader Impacts: For resource development, Dr. Cheung and her colleagues will provide constructs, seeds and antibodies to the community. The PIs routinely host and train postdoctoral, graduate and undergraduate students in their laboratories, and plan to continue to do so in the context of this project. Since 1997, Dr. Cheung has mentored approximately 40 undergraduates, including several from unrepresented ethnic groups, and there are currently undergraduates participating in on-going efforts related to the project. Dr. Kieliszewski also consistently supervises undergraduates in her laboratory. Many of these undergraduates have gone on to graduate school in the sciences. Besides the PIs themselves, postdocs and senior graduate students in the Cheung and Kieliszewski laboratories all contribute to the direct training of undergraduates, therefore providing them with mentoring and teaching experience in preparation for their own future career development. Overall, this research project will provide a broad spectrum of training areas on different levels of sophistication suitable for students at the undergraduate, graduate and postdoctoral level.