Developmental Regulation of Auxin Biosynthesis in Arabidopsis thaliana

9870798本项目的长期目标是了解生长素生物合成的发育调控。生长素是植物生长发育的关键调节因子，植物体内生长素水平的维持（生长素稳态）是一个动态的过程，它对发育和环境因素做出了显著的反应。由于生长素生物合成、代谢和信号转导的大多数方面尚未明确，生长素稳态与生长素生长发育效应之间的相互作用尚不清楚。生长素的生物合成一直是一个特别令人烦恼的问题，迄今为止，没有任何一种假设的植物生长素，吲哚-3-乙酸（IAA）的生物合成途径在任何植物物种中得到明确证明。拟南芥（Arabidopsis thaliana）是研究植物生长发育许多方面的优秀模型系统，本项目采用遗传、分子和生化技术相结合的方法来定义IAA在该植物中的生物合成并表征其发育调控。体内标记技术将用于确定IAA和那些被鉴定为IAA前体的化合物的合成和周转率。此外，还将检查IAA和前体池的细胞分布。这些基本信息将使研究者能够在IAA生物合成突变体的遗传筛选中确定候选突变体的特征，以及其他在IAA稳态中存在明显缺陷的突变体。这些将是确定IAA生物合成在控制生长和发育中的作用，并最终以农业上有用的方式操纵IAA生物合成的有价值的工具。有多种IAA生物合成途径利用色氨酸（色氨酸依赖途径）或其他化合物（色氨酸独立途径）作为前体。这些途径在发育过程中似乎被不同地利用。由于目前尚不清楚trp依赖途径和trp不依赖途径，因此本项目的直接目标如下：1。量化不同发育时间点IAA的合成和周转率，量化亚细胞前体和产物池的代谢活性。确定吲哚-丙酮酸（IPA）和/或吲哚-3-乙醛（IAAld）是否为IAA生物合成的中间体。鉴定IAA生物合成中的其他中间体。启动对色氨酸依赖性或非色氨酸依赖性IAA生物合成缺陷突变体的筛选。筛选拟南芥cdna转化酵母的吲哚代谢基因池。

9870798NormanlyThe long range goal of this project is to understand the developmental regulation of auxin biosynthesis. Auxin is a key regulator of plant growth and development, and it is known that the maintenance of auxin levels (auxin homeostasis) in the plant is a dynamic process that responds dramatically to developmental as well as environmental cues. The interplay between auxin homeostasis and the growth and developmental effects of auxin is still unclear since most aspects of auxin biosynthesis, metabolism, and signal transduction are poorly defined. The problem of auxin biosynthesis has been particularly vexing, and to date, none of the pathways that have been postulated for biosynthesis of the primary plant auxin, indole-3-acetic acid (IAA), has been proven definitively in any plant species. Arabidopsis thaliana is an excellent model system for the study of many aspects of plant growth and development and this project employs a combination of genetic, molecular, and biochemical techniques to define IAA biosynthesis and characterize its developmental regulation in this plant. In vivo labeling techniques will be used to determine synthesis and turnover rates for IAA and those compounds that are identified as IAA precursors. Additionally, the cellular distribution of IAA and precursor pools will be examined. This basic information will enable the investigator to characterize the candidates obtained in genetic screens for IAA biosynthetic mutants, as well as other mutants with apparent defects in IAA homeostasis. These will be valuable tools with which to define the role of IAA biosynthesis in the control of growth and development, and ultimately to manipulate IAA biosynthesis in agriculturally useful ways.There are multiple IAA biosynthetic pathways that utilize as a precursor either tryptophan (Trp-dependent pathways) or some other compound (Trp-independent pathways). These pathways appear to be utilized differentially during development. Since neither the Trp-dependent nor Trp-independent pathway is known, the immediate goals of this project are as follows:1. Quantify rates of IAA synthesis and turnover at different developmental time points and quantify metabolic activity of subcellular precursor and product pools.2. Establish whether indole-pyruvic acid (IPA) and /or indole-3-acetaldehyde (IAAld) are intermediates in IAA biosynthesis.3. Identify other intermediates in IAA biosynthesis.4. Initiate a screen for mutants defective in either Trp-dependent or Trp-independent IAA biosynthesis.5. Screen pools of yeast transformed with Arabidopsis cDNAs for indole-metabolizing genes.