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

智力优势：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生长素上调小基因家族的成员。尽管这些基因作为大基因家族在所有植物中似乎都存在并且高度保守，但实际上对于它们在生长素介导的生长和发育中所起的作用（如果有的话）一无所知。使用反向遗传方法，我们发现含有n端标签的拟南芥SAUR19家族成员的过表达赋予许多表型，表明生长素介导的生长受到干扰。相比之下，未标记的SAUR19过表达对植物生长发育无明显影响。Gray博士的研究结果表明SAUR19是一种高度不稳定的蛋白质，在SAUR19上添加n端标签对蛋白质具有稳定作用。迄今为止的研究得出的假设是，SAUR19在生长素介导的细胞扩增中起着至关重要的作用，可能是通过调节生长素的运输。本项目的目的是了解SAUR19及其密切相关的SAUR家族成员在生长素调控生长中的作用。将采用正向和反向遗传策略来阐明SAUR19的功能，表征SAUR19相互作用蛋白，并研究SAUR19转基因幼苗的生长素运输缺陷与已知生长素运输机制的关系。更广泛的影响：序列和表达分析表明，SAUR基因存在于所有植物中，包括苔藓、单子叶植物和双子叶植物。实际上，关于SAUR基因的功能我们一无所知。由于生长素在调节植物生长发育的许多方面起着核心作用，包括农业进口的一些性状，如生物量、结实和大小以及根系发育，因此阐明SAUR的功能对于理解生长素的作用至关重要，并且将引起广泛的兴趣。此外，这项工作也将有助于我们了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的广泛培训。此外，原创性研究和本科教育的整合是这个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 -葡糖醛酸酶报告程序分析SAUR基因的表达，并将这些信息汇集到一个在线的、可搜索的数据库中，该数据库将提供给植物研究界。该数据库的创建将作为Macalester大学计算机科学/生物信息学课程的项目学习作业，由联合项目负责人和他的同事Elizabeth shop博士教授。此外，每年将从麦卡莱斯特大学选出一名本科生，在夏季的几个月里在格雷实验室工作。这些学生将在Gray实验室与PI、co-PI、研究生和博士后密切互动，在那里他们将获得宝贵而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.