在局部非生物性胁迫引起的植物系统性反应中胞外ATP通过受体DORN1介导形成的“胞外ATP波”及其调控作用的研究

As multicellular organisms, plants have systemic responses to local abiotic stresses, which improve the resistance or acclimation of plants to environmental stresses. However, there are many important questions about the internal mechanisms and key events for such systemic responses. Based on the analyzation of the current researches and many characteristics of plant extracellular ATP and its receptor DORN1, plant extracellular ATP could play important rols in the initiation, transmission, and perception of the signals for the systemic responses of plants to local abiotic stresses. And, the features of extracellular ATP and DORN1 also make extracellular ATP have a potential to form autopropagating signals via cell-to-cell communication and thus mediate such systemic responses of plants. Moreover, due to these characteristics, in the plant systemic responses to local abiotic stresses, extracellular ATP could act as an upstream signaling and be more specific and sensitive than other related signaling molecules. Based on the reasons above, we propose an unknown but imporant mechanism as described below. In the systemic responses of plants to local abiotic stresses, there may exist an “extracellular ATP wave”, which is formed by extracellular ATP autopropagation dependent on the mediation via receptor DORN1. Such “extracellular ATP wave ” can travel from the stressed sites to the systemic sites and be involved in the regulation of the systemic responses of plants to local abiotic stresses. We believe that this research would further develop and expand the current knowledge about the internal mechanism of the plant systemic responses to local abiotic stresses. And, this research would be helpful in developing new understanding about the function of plant extracellular ATP and might provide some valued references for other related researches.

作为多细胞生命体，植物能对局部非生物性胁迫产生系统性反应，以更好的抵抗或适应环境压力，但其内在机理和关键环节尚有许多重要问题亟待解答。通过对现有研究的分析来看，胞外ATP及其受体的诸多特性使胞外ATP很可能在植物这种系统性反应的信号引发、传递和感知等环节中均扮演着重要的角色，同时也使胞外ATP具有以“自延伸”方式在细胞间进行传递并调节这种系统性反应的潜力，且其较之其它相关信号分子处于上游的位置并更加特异和敏感。据此，本项目提出一个尚未探索但很可能存在的重要机制：在局部非生物性胁迫引起的植物系统性反应中，胞外ATP通过其受体DORN1的介导，以“自延伸”方式形成了一种从胁迫位点向系统位点传递的“胞外ATP波”，并由此调控了植物的这种系统性反应。相信对该机制的探索将使植物这种系统性反应的内在机制得到更加充分和深入的认知，而这也将极大丰富对植物胞外ATP功能的理解并为其它相关研究提供重要的借鉴。

本项目利用生化和分子生物学手段，研究了在局部非生物性胁迫引起的植物系统性反应中，胞外ATP水平的时空变化特征和胞外ATP及其受体的生理学作用。研究发现，在拟南芥下胚轴被损伤后，植株中的被损伤组织、系统组织以及连接组织（被损伤组织和系统组织之间的组织）中均存在细胞外ATP水平上升的现象，说明拟南芥下胚轴损伤能够引起“胞外ATP波”的发生，这个“胞外ATP波”的传播速度快于已报道的“活性氧波”的速度。利用DORN1突变体和Apyrase等生化试剂发现，被损伤组织和系统组织中活性氧水平的上升依赖于胞外ATP受体以及从被损伤组织向系统组织传递的“胞外ATP波”。进一步地，在拟南芥中，对植物局部组织（或器官）进行损伤或根部盐胁迫所引起的植株中钙离子水平的系统性变化同样受到胞外ATP及其受体的调控。在菜豆植株中，单个叶片损伤所引起的植株中活性氧含量、过氧化氢酶和多酚氧化酶活性、以及丙二醛含量等多种生理参数的系统性变化均和细胞外ATP有关。上述研究表明，在局部非生物性胁迫引起的植物系统性反应中，胞外ATP及其受体DORN1在植物这种系统性反应的引发、形成、信号传递和感知等环节中扮演着重要的角色。我们也发现，植物所释放的细胞外ATP有可能作为一种液相中扩散性信号来介导植物细胞之间乃至植物之间的信息交流。同时，项目组构建了利用荧光共振能量转移和适体酶传感器对植物胞外ATP进行检测的技术，为该项目科学问题的进一步深入探索提供了重要的工具。此外，项目组也在植物的强光响应、伤和生长平衡性、生长发育等生理学过程中研究了胞外ATP的变化规律及其调控作用。上述结果较深层次地阐释了在局部非生物性胁迫引起的植物系统性反应中，植物细胞外ATP及其受体的生理学行为和作用，从全新的角度丰富了对植物细胞外ATP的认识，也进一步揭示了局部非生物性胁迫引起的植物系统性反应的信号调控机制。