Molecular Characterization of the AXR2 Gene of Arabidopsis

9307134 Estelle植物激素生长素或吲哚乙酸（IAA）在植物生长和发育中起着重要作用。 为了了解生长素作用的分子机制，埃斯特尔博士和他的同事们正在研究拟南芥中一组被称为生长素抗性基因的基因。 这些基因的突变会导致植物生长素抗性和一系列发育缺陷，这些缺陷似乎与生长素敏感性降低有关。 此外，每个生长素抗性基因的突变会改变对至少一种额外植物激素的敏感性。 据推测，这种交叉抗性是植物激素作用的综合性质的反映。 在这个奖项中，Estelle博士描述了研究生长素抗性基因AXR2功能的实验。 在这个基因中有两个显性突变已被确定。 先前的研究表明AXR2基因在生长素反应的早期起作用。 此外，对axr2突变体植物的组织学研究表明，AXR2基因在生长素调节的细胞伸长中具有重要作用。 确定了三个具体目标。 首先，研究人员将分析两种快速生长素反应，这被认为是生长素诱导细胞伸长的重要因素。 其次，他们将分离和表征AXR2基因的新等位基因。 他们利用这些突变体来获得对野生型基因功能的新见解。 第三，他们将通过定位克隆分离AXR2基因，并在分子水平上表征野生型和突变型等位基因。 近年来，分子和生物化学研究已经鉴定和部分表征了几种可能在生长素作用中起作用的蛋白质。 然而，很难确定这些蛋白质的生理作用。 遗传学方法有望为我们理解这一复杂问题做出独特的贡献。 对AXR2等植物生长素抗性基因的遗传学和分子生物学特性的研究，将为植物激素作用机制的研究提供重要的新信息。 ***

9307134 Estelle The plant hormone auxin or indole acetic acid (IAA) plays a central role in plant growth and development. To understand the molecular mechanism of auxin action Dr. Estelle and his colleagues are studying a group of genes in Arabidopsis thaliana called the auxin- resistance genes. Mutations in these genes cause auxin resistance and an array of developmental defects which appear to be related to a reduction in auxin sensitivity. In addition, mutations in each of the auxin-resistance genes alter sensitivity to at least one additional plant hormone. It is hypothesized that this cross resistance is a reflection of the integrated nature of plant hormone action. In this award, Dr. Estelle describes experiments which investigate the function of the auxin-resistance gene AXR2. Two dominant mutations in this gene have been identified. The prior studies suggest that the AXR2 gene functions early in auxin response. In addition, histological studies on axr2 mutant plants suggest that the AXR2 gene has an important role in auxin-regulated cell elongation. Three specific aims are defined. First, the investigators will analyze two rapid auxin responses which are thought to be important in auxin-induced cell elongation. Second, they will isolate and characterize new alleles of the AXR2 gene. They use these mutants to gain new insight into the function of the wild-type gene. Third, they will isolate the AXR2 gene by positional cloning and characterize both wild-type and mutant alleles at the molecular level. In recent years, molecular and biochemical studies have resulted in the identification and partial characterization of several proteins which may function in auxin action. However, it has been difficult to determine the physiological role of these proteins. A genetic approach promises to make a unique contribution to our understanding of this complex problem. It is expected that the genetic and molecular characterization of auxin-resi stance genes like AXR2 will provide important new information on the mechanism of hormone action. ***