EAGER: A novel mechanism for the regulation of cytokinin signaling in plants

细胞分裂素是调节许多重要农艺性状的植物激素，包括植物结构、生物量、衰老、抗病性、抗旱性和粮食产量。更好地了解细胞分裂素信号传导将使作物优化，以提高其在各种农业环境中的表现。本项目的目标是揭示细胞分裂素激素信号如何调节植物基因表达，从而控制植物生长发育。最先进的质谱方法将用于鉴定蛋白质的调节修饰以及这些修饰在细胞分裂素反应中如何变化。本项目将为研究生和博士后提供良好的培训机会。此外，通过当地的合作伙伴关系，该项目将建立一个暑期项目，旨在通过将科学与艺术相结合的参与性活动来发展教育和科学意识。目前的细胞分裂素信号转导范例涉及一个双组分的His-Asp磷酸化中继，类似于在原核生物中发现的。在这个模型中，保守的Asp残基上的b型反应调节因子（RRs）的磷酸化调节了它们的转录活性，从而控制了对细胞分裂素的转录反应。本项目的目的是验证b型RRs的Ser/Thr磷酸化也有助于调节其活性的假设。我们的预测是，细胞分裂素依赖性的丝氨酸/苏氨酸磷酸化将发生快速变化，这些变化将独立于Asp磷酸化激活b型反应调节因子。磷酸化蛋白质组学方法将用于鉴定b型反应调节因子的体内磷酸化位点，并表征其对细胞分裂素的磷酸化动力学。Ser/Thr磷酸化位点的调控意义将通过将残基突变为磷酰（Glu）和非磷酸化（Ala）版本来测试，并在报告系统中检测它们的活性。揭示b型RRs的Ser/Thr调控机制将从根本上改变我们关于细胞分裂素信号转导如何在植物中发生的模型，并为进化上古老的双组分信号通路如何适应真核生物的需要提供新的信息。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Cytokinins are plant hormones that regulate many agronomically important traits, including plant architecture, biomass, senescence, disease resistance, drought resistance, and grain yield. A better understanding of cytokinin signaling will enable optimization of crops to improve their performance in various agricultural settings. The goal of this project is to uncover how the cytokinin hormone signal regulates gene expression in plants, and thereby controls plant growth and development. State-of-the art mass spectrometry approaches will be used to identify regulatory modifications on proteins and how these modifications change during the cytokinin response. The proposed research will provide excellent training opportunities for graduate students and postdoctoral fellows. In addition, through a local partnership, the project will establish a summer program aimed at developing education and science awareness through participatory activities that integrate science with art.The current paradigm for cytokinin signaling involves a two-component His-Asp phosphorelay similar to that found in prokaryotes. In this model, phosphorylation of the type-B response regulators (RRs) on a conserved Asp residue regulates their transcriptional activity, thereby controlling the transcriptional response to cytokinin. The goal of this project is to test the hypothesis that Ser/Thr phosphorylation of the type-B RRs also serves to regulate their activity. The prediction is that rapid cytokinin-dependent changes in Ser/Thr phosphorylation will occur, and that these will activate the type-B response regulators independently of Asp phosphorylation. Phosphoproteomic approaches will be employed to identify in vivo phosphorylation sites of the type-B response regulators and to characterize their phosphorylation dynamics in response to cytokinin. The regulatory significance of Ser/Thr phosphorylation sites will be tested by mutating the residues to phosphomimic (Glu) and non-phosphorylatable (Ala) versions of the residues, and their activity examined in a reporter system. Uncovering a Ser/Thr regulatory mechanism for the type-B RRs will fundamentally alter our model as to how cytokinin signal transduction occurs in plants, and also yield novel information on how the evolutionarily ancient two-component signaling pathway has been adapted to the needs of a eukaryote.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.