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首页> 外文学位 >Analysis of the function and metabolism of indole-3-acetic acid conjugates in Arabidopsis thaliana.
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Analysis of the function and metabolism of indole-3-acetic acid conjugates in Arabidopsis thaliana.

机译：拟南芥中吲哚-3-乙酸结合物的功能和代谢分析。

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摘要

The auxin indole-3-acetic acid (IAA) is involved in virtually every aspect of plant development. Plants control auxin homeostasis through complex interactions between de novo synthesis, degradation, import, export, and conjugate synthesis and hydrolysis. A thorough knowledge of these pathways and their interactions is key to understanding auxin response and plant growth.; I have used genetic and biochemical methods to better understand the function and metabolism of amide-linked conjugates of IAA. Conjugates may function as storage or transport forms of IAA, or may function independently of hydrolysis. Many IAA conjugates have auxin activity in bioassays, and Arabidopsis mutants with reduced sensitivity to exogenous IAA-L-amino acid conjugates have been identified. Some of these are defective in genes encoding conjugate hydrolases, whereas others are likely to be directly or indirectly involved in some other aspect of conjugate metabolism or transport.; To better understand conjugate hydrolysis pathways, I have generated and screened an overexpression library to identify cDNAs that lead to conjugate resistance when overexpressed. From this library, I have identified one mutant that cosuppresses petH, resulting in a chlorotic phenotype, and several mutants resistant to IAA-Ala that result from mutations unlinked to T-DNA inserts. In addition, I have cloned the gene defective in iar4, an IAA-alanine-resistant mutant, and found that it encodes a protein similar to a mitochondrial pyruvate dehydrogenase E1α subunit. To better understand conjugate hydrolysis, I have characterized the enzyme activities of four members of the amidohydrolase family. I found that bacterially expressed GST fusions of ILR1, ILL2, and IAR3 hydrolyze certain IAA-amino acids with KM values in the μM range, suggesting they are physiologically relevant. In addition, mutant plant extracts show altered rates of conjugate hydrolysis, further supporting the hypothesis that these enzymes function in vivo to cleave IAA-amino acid conjugates. I have also examined the expression profiles of the amidohydrolase family and found their expression is overlapping but distinct. My findings suggest that the activity displayed by auxin conjugates is due to their hydrolysis by the amidohydrolases to yield free IAA, and that these processes are controlled both developmentally and spatially to regulate free IAA levels.
机译：生长素吲哚-3-乙酸（IAA）实际上涉及植物发育的每个方面。植物通过 de novo 合成，降解，导入，输出以及缀合物合成和水解之间的复杂相互作用来控制植物生长素的体内稳态。对这些途径及其相互作用的透彻了解是理解生长素反应和植物生长的关键。我已经使用遗传和生化方法更好地了解了IAA酰胺连接的偶联物的功能和代谢。缀合物可以充当IAA的存储或运输形式，或者可以独立于水解而起作用。许多IAA偶联物在生物测定中都具有生长素活性，并且已经鉴定出对外源IAA-L-氨基酸偶联物敏感度降低的拟南芥突变体。其中一些在编码缀合物水解酶的基因中有缺陷，而另一些则可能直接或间接地参与缀合物代谢或转运的其他方面。为了更好地理解共轭物的水解途径，我生成并筛选了一个过表达文库，以鉴定过表达时导致共轭抗性的cDNA。从该文库中，我确定了一个共抑制 petH 的突变体，其导致了褪绿型，以及几个对IAA-Ala产生抗性的突变体，这些突变是由与T-DNA插入片段无关的突变产生的。此外，我已经克隆了IAA-丙氨酸抗性突变体 iar4 中的缺陷基因，发现它编码的蛋白类似于线粒体丙酮酸脱氢酶E1α亚基。为了更好地理解缀合物水解，我对酰胺水解酶家族的四个成员的酶活性进行了表征。我发现，细菌表达的ILR1，ILL2和IAR3的GST融合蛋白会水解某些IAA氨基酸，其μM范围内的 K M 值，表明它们在生理上具有相关性。另外，突变的植物提取物显示出缀合物水解的速率改变，进一步支持了这些酶在体内起体内的作用来裂解IAA-氨基酸缀合物的假说。我还检查了酰胺水解酶家族的表达谱，发现它们的表达重叠但截然不同。我的发现表明，生长素结合物表现出的活性是由于它们被酰胺水解酶水解而生成游离IAA的结果，并且这些过程在发育和空间上均受到控制以调节游离IAA的水平。

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  • 作者

    LeClere, Sherry.;

  • 作者单位

    Rice University.;

  • 授予单位 Rice University.;
  • 学科 Biology Plant Physiology.; Biology Molecular.
  • 学位 Ph.D.
  • 年度 2002
  • 页码 152 p.
  • 总页数 152
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 植物学;分子遗传学;
  • 关键词

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