The Mechanism of Gibberellin-Induced Proteolysis of RGA in Arabidopsis

生物活性赤霉素（GAs）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、叶片膨大、茎伸长和花发育的作用。 在60年代和70年代的“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。 最近的研究表明，这些品种在其GA生产或GA反应的修改，说明GA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信号转导的两个主要阻遏物。 去除RGA和GAI功能允许GA非依赖性茎和叶生长和开花。 先前的研究表明，GA通过引起RGA和GAI的降解来激活其信号通路，并且拟南芥中GA信号的正调节因子SLY 1可能在响应GA信号而靶向RGA和GAI降解中起作用。 该建议旨在阐明GA诱导RGA蛋白水解的机制。 将采取一些生物化学方法来确定RGA和SLY 1是否在植物中相互作用。 RGA活性受蛋白水解控制，并且可能受蛋白质修饰（例如，磷酸化和/或糖基化）。 将采用蛋白质组学方法来鉴定该蛋白质中的修饰类型和位点。 然后将单独改变这些位点以检查修饰的位点在调节RGA活性和/或稳定性中的作用。半矮秆小麦品种是绿色革命的重要组成部分，在RGA/GAI的功能直系同源物（Rht基因座）中含有突变。 由于RGA/GAI的直系同源物在植物中高度保守，因此拟议工作的结果可能会对改善农作物质量产生广泛影响。 其他更广泛的影响包括培训本科生、研究生和博士后研究员，包括少数群体。 该项目的成果也将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.