MOLECULAR GENETICS OF AUXIN ACTION IN ARABIDOPSIS

植物生长素是植物生长和发育的各个方面所必需的。我们已经表明，生长素是需要连接的泛素样蛋白RUB到一个或多个细胞蛋白。在拟南芥中，RUB激活酶AXR 1-ECR 1和RUB缀合酶RCE 1参与RUB缀合。AXR 1基因的隐性突变或ECR 1的显性阴性版本的表达导致生长素反应降低。在植物、真菌和动物中，RUB与cullin蛋白家族的成员结合，包括S中的Cdc 53。酿酒酵母和AtCUL 1的表达。我们的研究表明，RUB修饰影响cullin的功能，而不是它的稳定性。在拟南芥的情况下，我们建议的RUB修改AtCUL 1影响SCFtiri，生长素反应所需的泛素蛋白连接酶的功能。在这个项目中，我们将继续我们的研究生长素的行动，调查这些异构体在体外和体内的功能。此外，存在至少两种不同的RUB蛋白。这两个分子在生长素反应中的功能将被确定。第二个目的是确认RUB修饰的AtCUL 1是生长素反应所必需的。在拟南芥中至少有两种额外的cullin蛋白，这些蛋白的功能将被研究。第三个目的是使用各种实验方法确定RUB修饰对AtCUL 1功能的影响。第四个目的是分离和表征SAR 1和AXR 4基因。遗传学研究表明，这两个基因在AXR 1-TIR 1通路中发挥作用。在第五个也是最后一个具体目标中，我们将对axr 1突变的几个新抑制因子进行遗传和表型表征。基于这些研究的结果，我们将分离和表征这些新基因中的一个或多个。我们期望这些研究结果提供重要的新信息的生长素反应的机制。此外，我们的研究将提供新的见解的高度保守的RUB共轭途径的功能，在所有的真核生物。

The plant hormone auxin is required for diverse aspects of plant growth and development. We have shown that auxin is requires conjunction of the ubiquitin-like protein RUB to one or more cellular proteins. In Arabidopsis, the RUB-activation enzyme AXR1-ECR1 and the RUB- conjugating enzyme RCE1 participate in RUB conjugation. Recessive mutations in the AXR1 gene or expression of a dominant-negative version of ECR1, result in reduced auxin response. In plants, fungi and animals, RUB is conjugated to members of the cullin family of proteins, including Cdc53 in S. cerevisiae and AtCUL1 in Arabidopsis. Our studies indicate that RUB modification affects the function of the cullin rather that its stability. In the case of Arabidopsis, we propose the RUB-modification of AtCUL1 affects the function of SCFtiri, a ubiquitin-protein ligase required for auxin response. In this project we will continue our studies of auxin action by investigating the function of these isoforms both in vitro and in vivo. In addition, there are at least two divergent RUB proteins. The function of these two molecules in auxin response will be determined. The second aim is to confirm that RUB-modified AtCUL1 is required for auxin response. There are at least two additional cullins in Arabidopsis and the functions of these proteins will be investigated. The third aim is to determine the effects of RUB-modification on AtCUL1 function using a variety of experimental approaches. The fourth aim is to isolate and characterize the SAR1 and AXR4 genes. Genetic studies indicate that both of these genes function in the AXR1-TIR1 pathway. In the fifth and last specific aim we will conduct the genetic and phenotype characterization of several novel suppressors of the axr1 mutation. Based on the results of these studies we will isolate and characterize one or more of these new genes. We expect the results of these studies to provide important new information on the mechanism of auxin response. In addition, our studies will provide new insight into the function of the highly conserved RUB- conjugated pathway in all eukaryote.