Auxin-Responsive Promoters and Auxin-Induced Growth

9303956 Guilfoyle植物激素，生长素，在细胞分裂、延伸和分化中发挥作用。Guillfoyle博士从大豆、豌豆和拟南芥中克隆了一些生长素反应基因(GH1、GH2/4、GH3和Saur)，这些基因在分生组织、伸长区内的表皮和皮质细胞、维管组织和/或发育中的木质部分子中表达。这些基因家族中的每一个都显示出不同的组织、器官和发育特定的表达模式。生长素反应基因产物的功能正在研究中。GH2/4基因编码谷胱甘肽S转移酶。这些基因的启动子正在转基因植物中进行分析，并通过基因枪轰击大豆和在胡萝卜细胞中瞬时表达来进行分析。推测的生长素反应元件(AuxREs)已经被鉴定出来，与AuxREs结合的转录因子正在被克隆。生长素反应启动子已被用于监测生长素在向向性、木质化、生根、开花和种子形成过程中的基因表达。这些启动子还被用于在转基因植物中驱动生长素和细胞分裂素生物合成基因以及生长素结合酶基因的表达。这些激素修饰基因在组织和器官中的特定表达导致植物生长和发育的许多变化，以及细胞命运的变化。激素水平改变的转基因植物正与拟南芥向重力突变体一起用于研究生长素反应基因表达的变化。Guilfoyle博士建议1)准确地确定哪些序列元件使一个基因对生长素作出反应；确定在不同的生长素反应基因中是否存在超过一种类型的AuxRE，并克隆和分析与AuxRE相互作用的转录因子；2)使用AuxRE或生长素反应启动子作为分子探针来研究生长素调节生长发育过程中的基因表达；使用过量生产或结合生长素或过度产生细胞分裂素的转基因植物作为工具来研究生长素调节的基因表达；3)深入了解生长素反应基因产物的功能及其在生长素作用中的可能作用；以及4)利用嵌合结构来鉴定生长素反应突变体；寻找生长素信号转导途径中的突变体(S)。这项研究的长期目标是了解生长素如何调节基因表达以及生长素受体信号如何传递到细胞扩张、细胞分裂和植物发育等事件；操纵生长素反应启动子、生长素反应基因产物和/或生长素或细胞分裂素生物合成基因以有益的方式改变植物的生长和发育。***

9303956 Guilfoyle The plant hormone, auxin, plays roles in cell division, extension, and differentiation. Dr. Guillfoyle has cloned a number of auxin responsive genes (GH1, GH2/4, GH3, and SAURs) from soybean, pea and Arabidopsis that are expressed in meristems, epidermal and cortical cells within elongation zones, vascular tissues, and/or developing xylem elements. Each of these gene families shows distinct tissue, organ, and developmental specific patterns of expression. The functions of the auxin responsive gene products are under investigation. The GH2/4 gene encodes a putative glutathione S- transferase. The promoters for these genes are being analyzed in transgenic plants and by particle gun bombardment of soybean and transient expression in carrot cells. Putative auxin responsive elements (AuxREs) have been identified and transcription factors that bind to the AuxREs are being cloned. The auxin responsive promoters have been used to monitor auxin regulated gene expression during tropisms, xylogenesis, rooting, flowering, and seed formation. These promoters have also been used to drive expression of auxin and cytokinin biosynthetic genes and a gene encoding an auxin conjugating enzyme in transgenic plants. The tissue and organ specific expression of these hormone modifying genes produces a number of changes in plant growth and development, as well as changes in cell fate. The transgenic plants with altered hormone levels are being used along with Arabidopsis gravitropic mutants to study alterations in expression of auxin responsive genes. Dr. Guilfoyle is proposing to 1) determine precisely what sequence elements make a gene auxin responsive; to determine if more than one type of AuxRE exists in different auxin responsive genes and to clone and analyze the transcription factors that interact with the AuxREs; 2) to use the AuxREs or auxin responsive promoters as molecular probes to study gene expression during auxin regulated growth and development; to use transgenic plants that overproduce or conjugate auxin or overproduce cytokinins as tools to study auxin regulated gene expression; 3) to gain insight into the functions of the auxin responsive gene products and their possible roles in auxin action; and 4) to take advantage of the chimeric constructs to identify auxin responsive mutants; to search for mutants in the auxin signal transduction pathway(s). The long range goals of this research are to understand how auxin regulates gene expression and how signals are transduced from the auxin receptor to events such as cell expansion, cell division, and plant development; to manipulate auxin responsive promoters, auxin responsive gene products and/or auxin or cytokinin biosynthetic genes to modify plant growth and development in beneficial ways. ***