线粒体ATP对细胞外ATP的调节作用参与水杨酸诱导植物抗病性和细胞死亡信号路径的研究

Salicylic acid plays an important role in inducing pathogen resistance and triggering cell death. A major focus in plant science is to uncover and describe the salicylic acid-mediated signaling pathway leading to the changes of physiological responses including pathogen resistance and cell death. Extracellular ATP, which originates from cytoplasmic ATP that is released into the extracellular milieu, has been defined in plants as an important signaling molecule to mediates intracellular responses by transmembrane receptors. Similar to the accumulation of salicylic acid, the last reports showed that decreases in the levels of extracellular ATP also can induce pathogen resistance and cell death in plants. Mitochondrial ATP, as most major resource of cytoplasmic ATP, determines the level of cytoplasmic ATP and thus would have important influence on the levels of extracellular ATP. Considering that the production of mitochondrial ATP is generally decreased by salicylic acid, it is expected that the levels of extracellular ATP would be decreased when mitochondrial ATP is decreased by salicylic acid.The observations and analysis above raise a possibility that salicylic acid can decrease mitochondrial ATP production and subsequently lead to a decline of extracellular ATP levels, which functions in inducing pathogen resistance and cell death by signaling pathway linking extracellular ATP perception to intracellular responses. This should be considered to be a novel but unknown mechanism which,as an important component, is involved in the salicylic acid-mediated signaling pathway leading to the changes of physiological responses including pathogen resistance and cell death. In addition, we believe that this research would further develope and expand the current knowledges about the functions of mitochondria and its production，ATP.

水杨酸是诱导植物抗病性和细胞死亡的重要信号，其信号路径机制始终是植物生理学研究的重点问题。细胞外ATP作为新发现的信号分子，能够通过受体介导作用调节植物的生理反应。且最新的研究发现，细胞外ATP的下降也能够诱导植物的抗病性和细胞死亡。细胞外ATP来自于细胞质ATP的向外释放；而线粒体ATP是细胞质ATP的主要来源，决定着细胞质ATP的水平，故也很可能对细胞外ATP的水平具有重大影响。线粒体ATP的产生会被水杨酸所降低，因此推测这也会引起细胞外ATP水平下降。基于此我们提出了一个与以往认识不同的水杨酸信号路径机制：水杨酸有可能通过降低线粒体ATP的产生而相应改变了细胞外ATP的水平，并由此通过细胞外ATP所介导的信号路径去诱导植物的抗病性和细胞死亡。这是一个尚未被探索但很可能存在的重要机制，并可能成为理解水杨酸调节植物生理反应信号通路的新的机理和环节；同时也将扩展对线粒体和ATP功能的认知。

细胞外ATP是能够调节植物生理反应的重要信号分子。通过本项目的实施，研究了水杨酸诱导植物细胞死亡过程中线粒体呼吸、细胞内ATP和胞外ATP的变化规律以及胞外ATP在水杨酸诱导植物细胞死亡过程中的调控作用及其内在机制；研究了水杨酸诱导线粒体呼吸、细胞内ATP生成、光合作用等生理学反应变化过程中胞外 ATP的生理学角色；研究了线粒体呼吸和细胞内ATP产生和胞外ATP水平之间的关系；研究了细胞外ATP对光合作用的调节作用；研究了细胞外ATP的调控作用和钙离子、过氧化氢等信号分子的关系；探讨了在植物细胞死亡过程中和植物被病原菌侵染等生物压力下，胞外ATP和水杨酸、钙离子、过氧化氢构成的信号应答网络以及细胞外ATP和线粒体呼吸、细胞内ATP、光合作用之间的关系机制。上述工作形成了调节植物生理反应信号通路的新的机理和环节，同时扩展了对ATP在植物细胞中功能的认知。