Molecular Genetics of Auxin Action in Arabidopsis

植物生长素在植物发育的许多方面都是必需的。生长素似乎刺激完整植物的细胞伸长和细胞分裂。生长素被认为是植物细胞生长所必需的，因为它是植物细胞在培养中生长所绝对需要的。尽管生长素很重要，但人们对其作用机制知之甚少。本研究旨在更好地确定生长素调控细胞事件的分子细节，为在整个植物水平上理解生长素调控发育奠定基础。本研究的重点是拟南芥，因为它特别适合于分子和经典遗传研究。参与生长素作用的基因将从对应用生长素没有正常反应的突变体中鉴定出来。以这种方式分离出的一种突变体被称为生长素抗性1或axr1。某些axr1突变植物已经在PI的实验室中被表征，突变体显示出许多缺陷，这表明生长素反应有缺陷。AXR1基因将被克隆并确定核苷酸序列。遗传学研究表明，该基因位于1号染色体上，与先前分离的DNA片段非常接近。这个DNA片段将被用来分离AXR1基因，使用一种叫做染色体行走的技术。一旦克隆成功，该基因将通过为拟南芥开发的植物转化程序导入axr1突变植株。在转化植株中失去生长素抗性将证实AXR1基因已被正确克隆。AXR1基因的DNA序列将被确定并用于推断基因产物的氨基酸序列，并将与其他先前分离的基因序列进行比较。分离的基因还可以确定植物中的哪些细胞正在制造AXR1基因产物。AXR1基因的分子特征将为植物生长素在植物发育中的作用提供重要的新见解。

The plant hormone auxin is required for many aspects of plant development. Auxin appears to stimulate cell elongation and cell division in intact plants. Auxin is thought to be essential for plant cell growth because it is absolutely required for growth of plant cells in culture. Despite its importance, very little is known about the mechanism of auxin action. This research proposes to better determine the molecular details of how auxin regulates cellular events as a basis for understanding auxin regulation of development at the level of the whole plant. The focus of this research is Arabidopsis thaliana because it is particularly well suited to both molecular and classical genetic studies. Genes involved in auxin action will be identified from mutants which do not respond normally to applied auxin. One of the mutants isolated in this way is called auxin resistant 1 or axr1. Certain axr1 mutant plants have been characterized in the PI's laboratory and the mutants display a number of defects which suggest defective auxin responses. The AXR1 gene will be cloned and the nucleotide sequence determined. Genetic studies have shown that the gene lies on chromosome one, very close to a previously isolated fragment of DNA. This fragment of DNA will be used to isolate the AXR1 gene using a technique called chromosome walking. Once cloned, the gene will be introduced into axr1 mutant plants using plant transformation procedures developed for Arabidopsis. Loss of auxin resistance in the transformed plants will confirm that the AXR1 gene has been correctly cloned. The DNA sequence of the AXR1 gene will be determined and used to deduce the amino acid sequence of the gene product and will be compared with the sequences of other previously isolated genes. The isolated gene will also allow determination of which cells in the plant are making the AXR1 gene product. The molecular characterization of the AXR1 gene should lead to important new insights into the role of auxin in plant development.