Molecular Mechanism of Gibberellin Signaling Repression by the DELLA Protein RGA in Arabidopsis

摘要赤霉素（Gibberellin， GA）是一种重要的植物生长激素，在高等植物中具有促进种子萌发、叶片膨胀、茎伸长和花朵发育的作用。上世纪60年代“绿色革命”期间培育的小麦和水稻矮秆品种显著提高了粮食产量。最近的研究表明，这些品种的GA产量或对GA的反应都经过了修饰，说明了这种激素在调节植物发育和农业中的重要作用。GA促进生长发育是由DELLA蛋白调控的，DELLA蛋白是GA反应的主要负调控因子（阻遏因子）。GA与受体结合后，通过引起DELLA的快速降解激活其反应途径。DELLA蛋白可能作为转录调控因子发挥作用，最近的研究发现了模式植物拟南芥中几个关键的DELLA调控基因。其中两个基因，一个编码转录调节因子（SCL3），另一个编码可能调节其下游靶蛋白稳定性的酶（RING）。研究人员将从遗传学、分子生物学和生物化学等方面探讨sc3和RING在ga调控的植物生长发育中的作用。DELLA蛋白在拟南芥和许多作物植物中功能高度保守。例如，作为绿色革命重要组成部分的半矮秆小麦品种，在编码DELLA蛋白的Rht位点中含有突变。这项研究可能会对提高农作物质量产生更广泛的影响。此外，一名博士后和四名本科生将在该项目中获得研究经验。本研究的结果将被纳入杜克大学的四门本科课程（包括一门实验课程）。学生将学会欣赏从模式植物系统研究中获得的信息如何用于改善农业实践和造福社会。

IOS-0641548 (Tai-ping Sun)Title: Molecular Mechanism of Gibberellin Signaling Repression by the DELLA Protein RGA in ArabidopsisAbstract Gibberellin (GA) is an important plant growth hormone, which promotes seed germination, leaf expansion, stem elongation and flower development in higher plants. The dwarf cultivars of wheat and rice developed during the 'Green Revolution' in the 60s remarkably increased the grain yields. Recent studies revealed that these cultivars are modified in their GA production or responses to GA, illustrating the important role of this hormone in regulating plant development and in agriculture. GA-promoted growth and development is modulated by DELLA proteins, which are major negative regulators (repressors) of GA responses. GA, upon binding to its receptor, activates its response pathway by causing rapid degradation of DELLA. DELLA proteins are likely to function as transcriptional regulators and recent studies identified several key regulatory genes that are targets of DELLA in the model plant Arabidopsis. Two of these genes, one encodes transcription regulator (SCL3) and the other encodes an enzyme (RING) that may regulate stability of its downstream target protein(s). Genetic, molecular and biochemical approaches will be taken to investigate functions of SCL3 and RING in GA-regulated plant growth and development. DELLA proteins are functionally highly conserved in Arabidopsis and in many crop plants. For example, the semi-dwarf wheat cultivars, an essential component of the Green Revolution, contain mutations in the Rht loci that encode DELLA proteins. This study will likely to have a broader impact in improving quality of agricultural crops. In addition, a postdoctoral fellow and four undergraduate students will gain research experience in this project. The findings of this study will be incorporated into four undergraduate courses (including one lab course) at Duke University. Students will learn to appreciate how the information gained from studies in a model plant system can be used to improve agriculture practice and benefit society.