Regulation of Gibberellin Biosynthesis in Arabidopsis

赤霉素（GA）类植物激素控制植物中的许多过程和发育事件，如种子萌发、茎生长、开花和果实发育。这些过程通常不是由GAs单独控制，而是由GAs与其他激素的相互作用控制。这项研究将探讨生长素是否可以对GA的生物合成产生调节作用，从而为这两种生长促进激素之间的相互作用提供一种机制。主要研究者实验室先前的工作导致分离出一种拟南芥突变体（以前称为10.3或ga 6），其茎生长减少，开花延迟和果实大小减小。 这些症状可以通过用某些GA处理突变体植物来克服，从而导致在该突变体中活性GA激素的生物合成被阻断的假设。现在已经知道，这种突变是等位基因的转运蛋白3（tir 3）突变，导致改变极性运输生长素。拟议的研究将检查生长素是否在GA生物合成途径的两个阶段发挥控制作用，即20-氧化和3b-羟基化。 由于编码这些生物合成酶的基因已被克隆，生长素对GA生物合成的可能影响将在基因表达水平上进行检查。 建议通过RNA印迹和使用报告基因融合来比较这些基因在野生型和tir 3植物中的表达。 还将检查改变的生长素反应1（axr 1）突变体，以查看这种突变是否也影响编码这些GA生物合成酶的基因的表达，所述突变显著降低植物对生长素的敏感性。 最后，野生型植物的生长素状态将被扰乱，并将检查对GA反应和GA生物合成酶基因表达的可能影响。这所大学是一所少数民族学生占多数的大学。 该研究计划提供了一个机会，为来自历史上在科学和技术方面代表性不足的群体的本科生提供植物生理学和生物化学实践方面的培训。

The gibberellin (GA) group of plant hormones controls many processes and developmental events in plants, such as seed germination, stem growth, flowering and fruit development. These processes are often not controlled by GAs alone, but by an interplay of GAs with other hormones. The proposed research will investigate whether auxin can exert a regulatory effect on GA biosynthesis, and thus provide one mechanism for cross-talk between these two types of growth promoting hormones. Previous work in the principal investigator's laboratory led to the isolation of a mutant of Arabidopsis thaliana (previously known as 10.3 or ga6) which had reduced stem growth, delayed flowering and reduced fruit size. These symptoms could be overcome by treatment of mutant plants with certain GAs, leading to the hypothesis that biosynthesis of active GA hormone was blocked in this mutant. It has now known that this mutation is allelic to the transport inhibitor3 (tir3) mutation, which leads to an alteration in polar transport of auxin. The proposed research will examine whether auxins exert control at two stages in the GA biosynthetic pathway, namely 20-oxidation and 3b-hydroxylation. Since the genes encoding these biosynthetic enzymes have been cloned, the possible effect of auxins on GA biosynthesis will be examined at the level of gene expression. It is proposed to compare the expression of these genes in wildtype and tir3 plants by RNA blotting, and by using reporter gene fusions. The altered auxin response 1 (axr1) mutant will also be examined to see if this mutation, which dramatically reduces the sensitivity of plants to auxin, also affects the expression of genes encoding these GA biosynthetic enzymes. Finally, the auxin status of wildtype plants will be perturbed pharmacologically, and possible effects on GA response and expression of genes for GA biosynthetic enzymes will be examined.The work will be carried out at the University of Texas at San Antonio. This University is one in which the majority of students are undergraduates from ethnic minorities. The research program presents an opportunity to provide training in practical aspects of plant physiology and biochemistry to undergraduates from groups who are historically under-represented in science and technology.