Regulation of Gibberellin Biosynthesis in Arabidopsis

赤霉素（GA）类植物激素控制着植物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。本研究将探讨生长素是否对赤霉素生物合成具有调控作用，从而为两种促生长激素之间的串扰提供一种机制。在首席研究员实验室之前的工作中，分离出了拟南芥（Arabidopsis thaliana）的一种突变体（以前称为10.3或ga6），这种突变体减少了茎的生长，延迟了开花时间，缩小了果实的大小。这些症状可以通过用某些GAs处理突变植株来克服，这导致了一种假设，即在该突变体中活性GA激素的生物合成被阻断。现在已经知道，这种突变是转运抑制剂3 （tir3）突变的等位基因，后者导致生长素极性转运的改变。本研究将探讨生长素是否在GA生物合成途径的两个阶段，即20-氧化和3b-羟基化中发挥控制作用。由于编码这些生物合成酶的基因已经被克隆，生长素对赤霉素生物合成可能产生的影响将在基因表达水平上进行研究。我们建议通过RNA印迹和报告基因融合来比较这些基因在野生型和tir3植物中的表达。改变的生长素反应1 （axr1）突变体也将被检测，看看这种突变是否会显著降低植物对生长素的敏感性，也会影响编码这些GA生物合成酶的基因的表达。最后，对野生型植物的生长素状态进行了药理学上的干扰，并探讨了对赤霉素应答和赤霉素生物合成酶基因表达的可能影响。这项工作将在圣安东尼奥的德克萨斯大学进行。这是一所以少数民族本科生为主的大学。该研究项目提供了一个机会，为来自历史上在科学和技术领域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.