OsGAPC1-HDT701通过组蛋白乙酰化修饰调控植物免疫及胁迫应答的机制分析

Plants control redox signals and epigenetic states to orchestrate their immunity to contend with pathogen invasion. Epigenetic marks like DNA methylation and histone modification reconstitute specific defense transcription circuits, which rapidly trigger host pathogen resistance. Nevertheless, it is as yet unknown how plants control histone acetylation during defense. .We have recently clarified the mechanism by which plants control histone acetylation to trigger fungal pathogen resistance. It was previously revealed that GTPase OsRac1 is a key regulator in rice immune responses. Preliminary data showed that the glycolytic enzyme OsGAPC1 participates in rice blast resistance and interacts with OsRac1. In rice immune responses, OsGAPC1 acts as a nitric oxide (NO) sensor that controls histone acetylation by regulating histone deacetylase HDT701. The present study indicates that the OsRac1-NO-OsGAPC1-HDT701 signaling module links a pattern recognition receptor and histone acetylation during defense. .NO contributes to various physiological processes and stress responses. Several stress conditions trigger the nuclear translocation of the glycolytic enzyme GAPDH. It has also been shown that the overexpression of deacetylase HDT701 enhances salt and drought tolerance. Based on this evidence, it is possible that the OsGAPC1-HDT701 module is a key stress tolerance regulator. The main objective of this project was to determine whether the OsGAPC1-HDT701 signaling module acts as a NO sensor to regulate histone acetylation under various stress conditions. In addition, three other objectives were proposed to validate the central hypothesis..The first goal was to understand the molecular mechanisms of OsGAPC1-HDT701 module-dependent immunity. The components of the OsGAPC1-HDT701 module are to be identified. An explanation will be sought for the mechanism by which this module regulates histone acetylation in the promoter regions of specific target genes during defense. Second, an attempt will be made to elucidate the three-dimensional structure of the OsGAPC1-HDT701 module and understand how it is activated. Third, it will be determined whether the OsGAPC1-HDT701 module is involved in the tolerance abiotic stress like drought, heat, and cold.

植物在免疫防御过程中主要通过控制细胞内氧化还原和表观遗传修饰如DNA甲基化和组蛋白修饰应对病原体的入侵，然而作为组蛋白修饰方式之一的组蛋白乙酰化与提高抗病性之间的机制仍不清楚。我们研究发现糖酵解酶OsGAPC1作为一种新的OsRac1蛋白相互作用因子和一氧化氮（NO）受体在水稻对稻瘟病菌的抗性中起到了正调控作用，其中组蛋白去乙酰化酶HDT701对OsGAPC1的乙酰化是整个通路的关键步骤；此外脱乙酰酶在过表达HDT701基因的情况下可以增强植物的耐盐及耐旱能力。基于以上发现我们将继续深入探讨OsGAPC1-HDT701复合物在不同胁迫条件下感受NO信号来调节组蛋白乙酰化进而影响植物免疫防御的分子机制，找出该复合物中与影响靶基因特定启动子区域乙酰化程度的功能域，进一步从三维结构上明晰该复合物在分子水平上的功能活性基础，为最终破译植物如何通过组蛋白的乙酰化应对病原体侵害的研究提供更多理论依据。

植物控制氧化还原信号和表观遗传状态，以协调其免疫力，应对病原体的入侵。第二信使一氧化氮（NO）促进S-亚硝基化，这是一种典型的基于氧化还原的翻译后修饰，蛋白质的S-亚硝基化会导致目标蛋白活性的增强或抑制。基于蛋白质组学方法，包括糖酵解酶GAPDH在内的各种蛋白质已被确认在防御过程中进行S-亚硝基化。在动物和植物中，GAPDH很可能作为压力传感器，因为在各种压力条件下都能观察到GAPDH的核转位，但它们在防御中的作用仍然不清楚。最近，Mengel等人表明，NO抑制组蛋白去乙酰化酶（HDACs）的活性，导致拟南芥中特定基因的组蛋白H3和H4的过度乙酰化，假设H3/H4乙酰化刺激基因表达。然而，这种HDAC调节的基本机制仍然不清楚。在这个项目中，我们揭示了植物通过调控组蛋白乙酰化引发对真菌病原体的抗病性。我们之前揭示了小GTP酶OsRac1在水稻免疫中起着关键的调节作用。在这里，我们发现糖酵素OsGAPC1是OsRac1的一个新的互作蛋白，它在抗击稻瘟病真菌方面起着积极作用。研究表明甲壳素诱导产生的NO会导致OsGAPC1的S-亚硝基化和核转位，因此OsGAPC1可能是监测NO水平的传感器。核OsGAPC1与组蛋白去乙酰化酶HDT701相互作用，提高了组蛋白H4K5的乙酰化水平和防御基因的表达，增强了对稻瘟病真菌的抗病性。这些结果表明，OsGAPC1作为一个NO传感器，在水稻免疫过程中控制组蛋白乙酰化以调节基因活性。我们的项目表明，OsRac1-NO-OsGAPC1-HDT701信号模块是连接模式识别受体和组蛋白乙酰化的关键模块。重要的是，以前大多数与防御过程中组蛋白修饰有关的工作都集中在 "免疫启动 "上，即植物或细胞对反复的生物或非生物压力变得敏感，导致在受到胁迫时更快和更有力地激活防御反应。我们的研究结果为早期防御反应期间组蛋白乙酰化的基本机制提供了新的启示。

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