Cellular Mecanisms Controlling CDPK-Mediated Auxin Signaling Pathway

植物钙依赖性蛋白激酶（CDPKs）具有钙传感器和钙效应的双重功能，并被认为参与细胞对外部和内部刺激的多种反应。然而，它们的确切生理功能仍然难以捉摸。利用基于原生质体的功能基因组学方法和基于RNA干扰的反向遗传学方法，研究人员发现了两种拟南芥CDPKs在生长素信号传导中的新功能，首次提供了将Ca2+信号传导与生长素作用联系起来的分子证据。CDPK双敲除突变体表现出严重的分生组织缺陷，抑制几个关键的分生组织调节因子，并在整个植物生命周期中表现出异常生长。基于这些结果，假设这两个CDPKs代表生长素和Ca2+信号传导和发育过程之间的“缺失环节”。本研究项目的长期目标是了解cdpk介导的生长素信号转导通路的机制和意义。这些数据将表明，在生长素刺激下，CDPK从质膜快速移动到细胞质溶胶是CDPK依赖的生长素信号传导的关键步骤。该项目的目的是确定和表征控制生长素依赖性CDPK易位的细胞机制。拟议的实验将在原生质体和幼苗中使用生长素响应报告的功能分析，结合基于荧光蛋白的生物成像，以确定cdpk介导的生长素信号是否涉及蛋白脂质修饰、磷酸化、囊泡运输和/或细胞骨架重塑。

Plant calcium-dependent protein kinases (CDPKs) have dual functions as calcium sensors and effectors, and are thought to be involved in multiple cellular responses to external and internal stimuli. However, their precise physiological functions remain elusive. Using a protoplast based functional genomics approach and RNA interference based reverse genetics, a novel function of two Arabidopsis CDPKs in auxin signaling was discovered, providing the first molecular evidence connecting Ca2+ signaling to the action of auxin. A CDPK double knockout mutant shows severe meristem defects, repression of several key meristem regulators, and exhibits abnormal growth throughout the plant life cycle. Based on these results, it is hypothesized that these two CDPKs represent a "missing link" between auxin and Ca2+ signaling, and developmental processes. The long-term goal of this research project is to understand the mechanisms and significance of the CDPK-mediated auxin signal transduction pathway. The data will show that a rapid movement of CDPK from the plasma membrane to the cytosol upon auxin stimulation is a crucial step for CDPK-dependent auxin signaling. The objective of this project is to identify and characterize cellular mechanisms controlling auxin-dependent CDPK translocation. The proposed experiments will use functional assays with an auxin-responsive reporter in both protoplasts and seedlings, combined with fluorescent-protein based bio-imaging to establish if CDPK-mediated auxin signaling involves protein lipid modification, phosphorylation, vesicle trafficking, and/or cytoskeleton remodeling.