细菌跨界感知植物细胞分裂素的信号转导和识别特异性的分子基础

Host recognition is the primary step during bacterial infection against plants or animals. Bacterial pathogens use receptor histidine kinases to perceive host chemicals or environmental stimuli and then to modulate the expression of virulence factors. Sponsored by the Youth Project of Natural Science Foundation, our previous research found that the receptor histidine kinase PcrK encoded by the phytopathogen Xanthomonas campestris specifically binds and senses plant hormone cytokinin. The protein phosphorylation process triggered by cytokinin was dissected. However, PcrK is a multiple-modular protein so that the interactions between different protein domains and their regulatory functions, especially the role of these signalling in determining specificity, remains unclear. This proposal aims to decipher the subtle functions of PcrK modules in sensing cytokinin. We will screen and identify additional signals recognized by the tandem PAS domains of PcrK; dissect the impact of PAS domain-triggered signaling on cytokinin recognition. In addition, the regulation of REC1 domain, which is not involved in PcrK-PcrR phosphorelay, will be investigated, with special reference to the REC1-protein interactions. Since cytokinin-family chemical is one of the ancient organic agents in the Earth, they play essential roles in inter-kingdom communication among various organisms. On the basis of understanding of PcrK signalling integration, more efforts will be made to analyze the molecular mechanisms to define the affinity and specificity between PcrK-cytokinin interactions, and illustrate the molecular process of the origin and evolution of receptor-hormone relationships. The results will reveal complexity of receptor histidine kinases in hormone signal perception, which will shed light on the understanding of functions and mechanisms of cytokinins in inter-kingdom communication.

寄主识别是病原细菌成功感染动、植物的首要步骤。细菌利用受体组氨酸激酶感知寄主和外界环境刺激并调控适应性反应。依托青年基金，前期研究发现植物病原细菌－野油菜黄单胞菌编码植物细胞分裂素受体PcrK，阐明了PcrK感应该植物激素后的磷酸化信号转导过程，但对识别刺激后的信号整合机制和特异性缺乏认识。本项目拟精细分析PcrK蛋白结构元件对植物激素信号感知功能的影响：鉴定PcrK的PAS结构域感应的其它信号刺激，研究该信号通路对植物细胞分裂素感应的影响；解析PcrK的REC1结构域在信号感知中的作用；研究PcrK整合多个信号输入的分子机制。在明确信号整合机制的基础上，深入分析PcrK识别细胞分裂素类化合物的亲合力和特异性，阐明受体－激素相互作用关系和功能进化的分子基础。研究成果将揭示受体组氨酸激酶信号识别功能的复杂性，为理解细胞分裂素类化合物在生物跨界信号交流中的功能、机制做出创新发现。

寄主识别是病原细菌成功感染的首要步骤，细菌利用受体蛋白感知宿主和环境信号。项目精细分析了受体蛋白PcrK各蛋白元件对其感知植物激素的影响，鉴定了PAS结构域感知的特异性信号，研究了PcrK各蛋白元件间的信号整合机制，深入分析了PcrK识别植物细胞分离素的亲合力和特异性，阐明了受体-激素相互作用关系和功能进化的分子基础。我们完成了项目设定的研究目标和研究内容，鉴定到PAS结构域特异性识别宿主氧化还原信号，调控细菌运动；REC1结构域通过与蛋白互作发挥作用；各元件间相互协调，对于PcrK的功能发挥都是必不可少的；来自不同物种的CHASE结构域蛋白与细胞分裂素间的互作分析表明受体识别跨界信号与病原菌适应宿主环境相关。共发表SCI论文2篇，授权专利1项，培养博士后1名，硕士和博士研究生各2名，青年科研人才2人次。