Modulation of light signalling by the response regulator ARR4 and other two-component signalling elements

双组分系统（TCS）是一种磷酸转移机制，赋予感知和响应外源性或内源性刺激的能力。在高等植物中，TCS通常包括三个元件：杂合组氨酸激酶、含组氨酸的磷酸转移域蛋白和反应调节子。在过去的几年里，双组分信号系统已经被深入研究，特别是在激素信号。我们最近在拟南芥中进行的分析表明，TCS也作为一种分子机制，整合内源（如植物激素）和环境（如光）信号，以优化影响植物生长，发育和适应环境条件。例如，响应调节剂ARR 4能够稳定光敏色素B的活性Pfr形式，从而改变红光依赖性光形态建成。在拟议的研究中，我们希望在现有成果的基础上继续我们的工作。因此，我们将集中在拟南芥中ARR4与光信号转导相互作用的分子和功能方面。这包括（i）详细分析arr4突变体和ARR4过表达系的生理特性，（ii）确定ARR4与phyB功能性相互作用发生的细胞内位置，和（iii）鉴定调节ARR4活性的上游信号和TCS元件。为此，我们将使用最先进的分子、细胞生物学、生物化学和生理学工具。

The two-component system (TCS) is a phosphotransfer mechanism that confers the ability to sense and respond to exogenous or endogenous stimuli. In higher plants, TCS usually com-prises three elements: a hybrid histidine kinase, a histidine-containing phosphotransfer do-main protein and a response regulator. In the past years two-component signalling systems have been intensively studied especially in hormone signalling. Recent analyses performed by us in Arabidopsis plants indicate that TCS also functions as a molecular mechanism that integrates endogenous (e.g. phytohormones) and environmental (e.g. light) signals to opti-mally influence plant growth, development and adaptation to environmental conditions. For instance, the response regulator ARR4 is able to stabilize the active Pfr form of phytochrome B and thereby modifies red light dependent photomorphogenesis. In the proposed research we would like to continue our work on the basis of existing results. We will thereby concentrate on the molecular and functional aspects of the interaction of ARR4 with light signal transduction in Arabidopsis. This includes (i) detailed analysis of the physiological properties of arr4 mutants and ARR4 overexpressing lines, (ii) determination of the intracellular location, at which the interaction of ARR4 with phyB functionally occurs and (iii) identification of upstream signals and TCS elements regulating ARR4 activity. For this purpose, we will use state-of-the-art molecular, cell biological, biochemical and physiological tools.