Functional characterization of the two-component signaling system of Arabidopsis

本课题旨在研究拟南芥双组分信号系统（TCS）将信号信息转化为生物学过程的分子机制。在高等真核生物中，TCS是植物所特有的。拟南芥基因组编码8种杂交传感器激酶（AHKs）、5种组氨酸磷酸转移蛋白（AHPs）和22种不同类型的应答调节因子（a型和b型ARRs）。TCS感知和传递细胞分裂素信号，在调控根、梢生长、种子发育和衰老中起重要作用。在之前的资助期内，我们克隆了大部分TCS基因，建立了TCS蛋白-蛋白相互作用图谱，鉴定了与其他拟南芥蛋白的相互作用，构建了TCS显性阴性转录因子，鉴定了一组主要靶基因，并对细胞分裂素受体突变体进行了详细的研究。这些结果为当前的提案设定了框架，其中我们遵循两个主要的研究方向。目的之一是了解选定的TCS蛋白相互作用的功能相关性，特别是细胞分裂素受体和b型ARRs的相互作用。第二个目的是研究b型arr的转录调控。这包括它们三个亚类的功能研究，它们的DNA靶序列的鉴定以及它们启动的部分转录级联的功能分析。对TCS功能的研究提供了对信号网络的示例性分析，从而解决了AFGN计划的一个重要主题。

The objective of the proposal is to study the molecular mechanisms used by the two-component signaling system (TCS) of Arabidopsis to convert signal information into biological processes. Among higher eukaryotes, the TCS is unique to plants. The Arabidopsis genome encodes eight hybrid sensor kinases (AHKs), five histidine phosphotransfer proteins (AHPs) and 22 response regulators of two different types (A-type and B-type ARRs). The TCS perceives and transmits cytokinin signals and has a major role in regulating root and shoot growth, seed development and senescence. In the previous funding period we cloned most of the TCS genes, established a protein-protein interaction map for the TCS, identified interactions with other Arabidopsis proteins, constructed a dominant-negative TCS transcription factor, identified a set of primary target genes and carried out a detailed study of cytokinin receptor mutants. These results set the framework for the current proposal in which we follow two major lines of research. One aim is to understand the functional relevance of selected interactions of TCS proteins, in particular those of the cytokinin receptors and B-type ARRs. A second aim is to study transcriptional regulation by B-type ARRs. This includes functional studies of their three subclasses, identification of their DNA target sequences and the functional analysis of part of the transcriptional cascade they initiate. The study of the TCS functions presents an exemplary analysis of a signaling network and thus addresses an important topic of the AFGN program.