Functional Analysis of Small Auxin Up-Regulated (SAUR) Genes in Arabidopsis

智力价值：植物激素生长素通过调节数百个基因的表达来调节生长和发育的许多方面。生长素诱导最迅速和最强烈的基因是小生长素上调(SAUR)基因家族的成员。虽然这些基因似乎在所有植物中都存在，并作为大基因家族高度保守，但几乎不知道它们在生长素介导的生长和发育中扮演什么角色。使用反向遗传方法，我们发现含有N-末端标签的拟南芥SAUR19家族成员的过度表达赋予了许多指示受干扰的生长素介导的生长的表型。相反，过表达未标记的SAUR19对植物的生长发育没有明显的影响。格雷博士的发现表明，SAUR19是一种高度不稳定的蛋白质，在SAUR19中添加N端标签对该蛋白质具有稳定作用。到目前为止的研究导致了这样的假设，即SAUR19在生长素介导的细胞扩张中发挥关键作用，可能是通过调节生长素运输来实现的。该项目的目标是了解SAUR19及其密切相关的SAUR家族成员在生长素调节生长中的功能。正向和反向遗传策略将被用来阐明SAUR19的功能，鉴定SAUR19相互作用的蛋白，并研究SAUR19转基因幼苗的生长素运输缺陷与生长素运输机制的已知成分的关系。广泛的影响：序列和表达分析表明，SAUR基因在所有植物中都以多基因大家族的形式存在，包括苔藓、单子叶和双子叶植物。关于SAUR基因的功能，人们几乎一无所知。由于生长素在植物生长和发育的许多方面起着核心作用，包括生物量、座果率和大小以及根系发育等几个农业重要特征，因此阐明SAUR的功能对于理解生长素的作用是必要的，并将具有广泛的意义。此外，预计这项工作也将有助于我们理解植物和其他真核生物中蛋白质稳定性的调节。该项目将为一名研究生和一名博士后提供支持，他们都将获得遗传学、分子和细胞生物学方法方面的广泛培训。此外，原创研究和本科教育的整合是该项目不可或缺的组成部分。Paul Overvoorde博士和他在Macalester学院的本科生将在这个项目中发挥重要作用。Overvoorde博士课程的学生将使用启动子-β-葡萄糖醛酸酶记者来分析SAUR基因的表达，并将这些信息汇编成一个在线的、可搜索的数据库，供植物研究社区使用。该数据库的建立将作为Macalester学生在计算机科学/生物信息学课程中以项目为基础的学习任务，该课程由该合作者及其同事Elizabeth Shoop博士讲授。此外，来自Macalester的一名本科生将被选为每年夏季几个月在Gray实验室工作的学生。这些学生将与格雷实验室的PI、共同PI、研究生和博士后密切互动，在那里他们将获得宝贵的和独特的植物分子遗传学研究经验。

Intellectual Merit: The plant hormone auxin regulates many aspects of growth and development by modulating the expression of several hundred genes. Among the most rapidly and strongly auxin-induced genes are members of the Small Auxin Up-Regulated (SAUR) gene family. Although these genes appear to be present and are highly conserved as large gene families in all plants, virtually nothing is known regarding what role, if any, they play in auxin-mediated growth and development. Using a reverse genetic approach, we have found that overexpression of members of the Arabidopsis SAUR19 family containing N-terminal tags confers numerous phenotypes indicative of perturbed auxin-mediated growth. In contrast, overexpression of untagged SAUR19 results in no obvious affects on plant growth and development. Dr. Gray's findings suggest that SAUR19 is a highly unstable protein and the addition of an N-terminal tag to SAUR19 has a stabilizing effect on the protein. Studies to date lead to the hypothesis that SAUR19 plays a crucial role in auxin-mediated cell expansion, perhaps by functioning as a regulator of auxin transport. The goal of this project is to understand the function of SAUR19 and closely related SAUR family members in auxin regulated growth. Both forward and reverse genetic strategies will be employed to elucidate SAUR19 function, characterize SAUR19 interacting proteins, and investigate the auxin transport defect of SAUR19 transgenic seedlings in relationship to known components of the auxin transport machinery.Broader Impacts: Sequence and expression analyses suggest that SAUR genes are present as large multigene families in all plants, including mosses, monocots, and dicots. Virtually nothing is known regarding the function of the SAUR genes. Since auxin plays a central role in regulating many aspects of plant growth and development, including several traits of agricultural import such as biomass, fruit set and size, and root system development, elucidation of SAUR functions is essential for understanding auxin action, and will be of broad interest. Additionally, it is expected that this work will also contribute to our understanding of the regulation of protein stability in plants and other eukaryotes. This project will provide support for one graduate student and one postdoc, both of whom will obtain broad training in genetics, molecular and cellular biological approaches. Additionally, integration of original research and undergraduate education is an integral component of this project. Dr. Paul Overvoorde and his undergraduate students at Macalester College will play vital roles in this project. Students in Dr. Overvoorde's courses will analyze the expression of SAUR genes using promoter-beta-glucuronidase reporters and will assemble this information into an online, searchable database that will be made available to the plant research community. The creation of this database will be used as a project-based learning assignment for Macalester students in computer science/bioinformatics courses taught by the co-PI and his colleague, Dr. Elizabeth Shoop. Additionally, one undergraduate student from Macalester will be selected each year to work in the Gray lab over the summer months. These students will interact closely with the PI, co-PI, and grad students and postdocs in the Gray lab where they will obtain a valuable and unique research experience in plant molecular genetics.