Functional characterization of the two-component signaling system of Arabidopsis

本研究的目的是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个杂交传感激酶（AHK），5个组氨酸磷酸转移蛋白（AHPs）和22个两种不同类型的反应调节因子（A型和B型ARR）。TCS感知并传递细胞分裂素信号，在调节根和芽的生长、种子发育和衰老中起主要作用。在上一个资助期，我们克隆了大部分的TCS基因，建立了一个蛋白质-蛋白质相互作用的TCS图谱，确定了与其他拟南芥蛋白质的相互作用，构建了一个显性负TCS转录因子，确定了一组主要的靶基因，并进行了详细的研究细胞分裂素受体突变体。这些结果为我们目前的建议设定了框架，我们遵循两条主要的研究路线。一个目的是了解TCS蛋白，特别是细胞分裂素受体和B型ARR的选择性相互作用的功能相关性。第二个目的是研究B型ARRs的转录调控。这包括它们的三个亚类的功能研究，它们的DNA靶序列的鉴定和它们启动的部分转录级联的功能分析。TCS功能的研究提出了一个信令网络的示例性分析，从而解决了AFGN计划的一个重要课题。

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.