The Mechanism of Gibberellin-Induced Proteolysis of RGA in Arabidopsis

生物活性赤霉素（bioactive gibberellins, GAs）是促进高等植物种子萌发、叶片扩张、茎伸长和花发育的重要植物生长激素。在60年代和70年代“绿色革命”期间开发的小麦和水稻矮秆品种显著提高了粮食产量。近年来的研究表明，这些品种在赤霉素生产或赤霉素响应方面发生了修饰，说明赤霉素在调节植物发育和农业中的重要作用。RGA和GAI蛋白是模式植物拟南芥中GA信号的两个主要抑制因子。去除RGA和GAI功能允许ga独立的茎和叶生长和开花。以往的研究表明，GA通过引起RGA和GAI的降解来激活其信号通路，而拟南芥中GA信号的正调节因子SLY1很可能响应GA信号，靶向RGA和GAI降解。本研究旨在阐明ga诱导RGA蛋白水解的机制。许多生物化学方法将被用来确定RGA和sle1是否在植物中相互作用。RGA活性受蛋白质水解和可能的蛋白质修饰（如磷酸化和/或糖基化）控制。将采用蛋白质组学方法来确定该蛋白质的修饰类型和位点。然后，这些位点将被单独改变，以检查修改后的位点在调节RGA活性和/或稳定性方面的作用。作为绿色革命的重要组成部分，半矮秆小麦品种含有RGA/GAI （Rht位点）功能同源突变。由于RGA/GAI同源基因在植物中高度保守，因此本研究的结果可能对提高农作物质量产生广泛的影响。其他更广泛的影响包括培养本科生、研究生和博士后，包括少数民族。该项目的成果也将被纳入杜克大学的本科课程。

PROJECT ABSTRACT for IBN-0348814Bioactive gibberellins (GAs) are important plant growth hormones, which promote 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 and 70s remarkably increased grain yields. Recent studies revealed that these cultivars are modified in their GA production or GA response, illustrating the important role of GA in regulating plant development and in agriculture. The RGA and GAI proteins are two major repressors of GA signaling in the model plant Arabidopsis. Removing both RGA and GAI functions allows for GA-independent stem and leaf growth and flowering. Previous studies illustrated that GA activates its signaling pathway by causing degradation of RGA and GAI and that SLY1, a positive regulator of GA signaling in Arabidopsis, is likely to play a role in targeting RGA and GAI for degradation in response to the GA signal. This proposal is aimed at elucidating the mechanism of GA-induced proteolysis of RGA. A number of biochemical approaches will be taken to determine whether RGA and SLY1 interact in planta. RGA activity is controlled by proteolysis, and possibly by protein modification (e.g., phosphorylation and/or glycosylation). A proteomic approach will be taken to identify the type(s) and site(s) of modification in this protein. These sites will then be altered individually to examine the role(s) of the modified sites in regulating RGA activity and/or stability. The semidwarf wheat cultivars, an essential component of the Green Revolution, contain mutations in the functional ortholog of RGA/GAI (the Rht loci). Because the orthologs of RGA/GAI are highly conserved in plants, the results from the proposed work will likely to have a broad impact in improving quality of agricultural crops. Additional broader impacts include the training of undergraduates, graduate students and postdoctoral fellows, including minorities. The results of the project will also be incorporated into undergraduate courses at Duke.