光呼吸GLO与CAT互作/解离调控机理及其与植物抗逆性的关系研究

Our previous work has demonstrated that up-regulating glycolate oxidase (GLO) conferred improved photosynthesis in rice under high light & high temperature conditions, and salicylic acid (SA) may be involved in the signaling process (Cui et al., 2016). Mechanistic analyses further revealed that in both rice and Arabidopsis, GLO was able to interact with catalase (CAT), and the interaction could be deregulated by SA, such that a switch model was proposed considering that association–dissociation of GLO with CAT may serve as a potential switch to modulate intracellular H2O2 levels (Zhang et al., 2016 and unpublished data). But more evidences are needed to make the model more convincing and finalized. In this project, we aim to in depth investigate that (i) regulatory factors/mechanism for association–dissociation of the GLO–CAT complex; (ii) contribution extent of the GLO–CAT modulated H2O2 to overall H2O2 signaling pathway and its possible different roles as compared with other sources of H2O2; (iii) whether and how the association-dissociation is related with stress resistance. Answering these questions may lead to discovery of a novel H2O2 genesis pathway characteristic of classical physiochemical mechanism, which will add new contributions to both signal transduction network, and function/mechanism of photorespiration in plants.

我们的前期研究发现，上调光呼吸乙醇酸氧化酶（GLO）可显著提高水稻高光高温双重胁迫下的光合效率，水杨酸（SA）可能参与其信号调节过程（Cui et al., 2016）。进一步研究发现，GLO可与过氧化氢酶（CAT）互作，且其互作能被SA解除，因此提出一个GLO-CAT互作/解离的动态开关模型，认为其互作/解离受环境因子动态调控，由此激发出H2O2震荡波来调节植物抗逆性反应 (Zhang et al., 2016)。但该模型还需进一步证实与完善，本项目拟深入了解：（1）GLO–CAT互作/解离的调控因子及机理；（2）互作/解离对H2O2信号通路贡献大小及可能的作用差异；（3）互作/解离与植物抗逆性的关系及机理。解答上述问题，以期确立一个具有典型物理化学特征的植物H2O2信号发生的新机理，这将对植物信号转导机理研究和光呼吸功能及作用机制研究产生重要影响，可望获得意义深远的原创性成果。

活性氧（ROS）在植物多种重要生物学过程中发挥着信号分子的作用，其含量受到严格的调控。现有研究表明ROS的精准调控主要依赖于其生成与清除的动态平衡，近期在ROS信号传导研究中提出的ROS信号波的概念更是引起了人们的广泛关注。我们的前期研究发现，上调光呼吸乙醇酸氧化酶（GLO）可显著提高水稻高光高温胁迫下的光合效率，水杨酸（SA）可能参与该调节过程；进一步研究发现，在细胞水平GLO可与过氧化氢酶（CAT）互作，且其互作能被SA解除，因此提出一个GLO-CAT互作/解离的动态开关模型，认为其互作/解离可能受环境因子动态调控，由此激发出H2O2信号波来调节植物抗逆性反应。本项目在此基础上进一步发现GLO与CAT存在直接互作，两者的互作较为松散，且可在不同互作强度状态间相互转变。在响应外界环境刺激时（如SA等），GLO-CAT可在植株水平发生动态可逆的互作/解离，而且GLO-CAT互作状态的变化与植株过氧化物酶体光呼吸H2O2含量变化紧密偶联。我们后续的离体实验证实GLO与CAT在互作时确实可形成H2O2代谢通道以提高H2O2清除效率，而两者的解离则可使得H2O2积累。GLO-CAT这一物理性的互作/解离机制可使得植物形成依赖于光呼吸代谢的H2O2信号波，该研究为H2O2信号波的发生提供了新的机理，同时也为H2O2与SA信号途径的交联互作提供了新的切入点。