Composite Auxin Response Elements and the Auxin Signal Transduction Pathway

[604208]植物激素生长素参与或控制多种发育过程。生长素诱导的细胞分裂、细胞伸长和细胞分化都涉及不同的基因表达模式。在这些生长发育过程中，已经发现了多种由生长素特异性诱导的早期或初级应答基因。在没有外源生长素的情况下，大多数早期生长素反应基因以组织特异性和器官特异性的方式表达。为了观察外源性生长素对这些基因的实质性诱导，通常需要首先将切除的器官浸泡在不含生长素的培养基中以消耗生长素。大豆GH3是一种早期生长素反应基因，在四个重要方面与其他基因不同。首先，在没有外源生长素的情况下，它的表达水平非常低。其次，GH3 mRNA可以在幼苗和植物中被诱导至少50倍，而无需对切除的器官进行生长素耗尽处理。第三，这种基因几乎可以在幼苗或植物的每一个细胞、组织或器官中被诱导。第四，无论是在原生质体中还是在稳定的转化体中，GH3启动子都对生长素有很高的响应。GH3基因启动子由转录起始位点250个碱基对内至少三个独立的生长素反应元件（AuxRE）组成，这些元件具有独立的功能、组织/器官特异性表达、DNA序列和生长素反应性等特征。此外，已经构建了与天然AuxREs或整个GH3启动子的诱导能力相当或多倍的新型AuxREs，并克隆了特异性结合复合AuxREs的转录因子。本研究将使用天然复合和更活跃的合成AuxREs来精确确定AuxREs在生长素响应启动子中的作用，并鉴定与复合AuxREs相互作用的转录因子并确定其作用机制。植物激素生长素参与或控制多种发育过程。生长素诱导的细胞分裂、细胞伸长和细胞分化都涉及不同的基因表达模式。在这些生长发育过程中，已经发现了多种由生长素特异性诱导的早期或初级应答基因。大豆GH3是一种早期生长素反应基因，几乎在幼苗或植物的每个细胞、组织或器官中都能被诱导。GH3基因的调控区（启动子）由至少三个独立的生长素反应元件（AuxRE）组成，这些元件在独立功能、组织/器官特异性表达、DNA序列和生长素反应性方面具有特征。此外，已经构建了与天然AuxREs活性相当或几倍的新型AuxREs。本研究将使用天然合成和更活跃的合成AuxREs来精确确定AuxREs的功能，并识别与AuxREs相互作用的转录因子并确定其作用机制。

9604208 Guilfoyle The plant hormone auxin is involved in or controls a wide variety of developmental processes. Auxin-induced cell division, cell elongation and cell differentiation all involve distinct patterns of gene expression. A variety of early or primary response genes that are specifically induced by auxin have been identified in these growth and developmental processes. Most of the early auxin response genes are expressed in a tissue-specific and organ-specific manner in the absence of exogenous auxin application. To observe a substantial induction of these genes by exogenous auxin, it generally is necessary first to deplete auxin by bathing excised organs in auxin-free medium. Soybean GH3 is an early auxin response gene that differs from others in four important ways. First, it is expressed at very low levels in the absence of exogenous auxin application. Second, GH3 mRNA can be induced at least 50-fold in seedlings and plants without subjecting excised organs to the auxin depletion protocol. Third, the gene is induced in virtually every cell, tissue or organ of a seedling or plant. Fourth, the GH3 promoter is highly responsive to auxin in a variety of heterologous plant species whether assayed transiently in protoplasts or in stable transformants. The GH3 gene promoter consists of at least three separate auxin response elements (AuxRE) within 250 base pairs of the transcription start site, which have been characterized with respect to independent function, tissue/organ-specific expression, DNA sequence, and auxin responsiveness. Moreover, novel AuxREs have been constructed that are equivalent or several fold more inducible by auxin than natural AuxREs or the entire GH3 promoter, and transcription factors have been cloned that bind specifically to composite AuxREs. This research will use both natural composite and more active synthetic AuxREs to precisely determine how AuxREs function in auxin-responsive promoters, and to identify transcription factors that interact with composite AuxREs and determine their mechanism of action. The plant hormone auxin is involved in or controls a wide variety of developmental processes. Auxin-induced cell division, cell elongation and cell differentiation all involve distinct patterns of gene expression. A variety of early or primary response genes that are specifically induced by auxin have been identified in these growth and developmental processes. Soybean GH3 is an early auxin response gene that is induced in virtually every cell, tissue or organ of a seedling or plant. The regulatory region (promoter) of the GH3 gene consists of at least three separate auxin response elements (AuxRE) which have been characterized with respect to independent function, tissue/organ-specific expression, DNA sequence, and auxin responsiveness. Moreover, novel AuxREs have been constructed that are equivalent or several fold more active than natural AuxREs. This research will use both natural composite and more active synthetic AuxREs to precisely determine how AuxREs function, and to identify transcription factors that interact with AuxREs and determine their mechanism of action.