新型气体信号分子硫化氢（H2S）增强植物耐受水涝低氧胁迫机制的研究

Hydrogen sulfide (H2S) is a highly diffusible, gaseous signal molecule. A number of studies in animal and plant cells have centered upon its effect on many biological processes. It is notably that H2S acts as a oxygen sensor in response to hypoxia signaling in animal. However, there have been no previous studies of H2S in response to hypoxia in plant cells. Recently, our experimental results demonstrated that exogenous H2S pretreatment could obviously improve the hypoxia tolerance ability in pea seedlings, maize and Arabidopsis under hypoxia conditions, however, the exact mechanism is still unknown. In this project, the effects of H2S on hypoxia-induced cell death and interactions between H2S and reactive oxygen species (ROS) will be studied; whether the ER stress is involved in H2S signaling will be analyzed in maize and Arabidopsis mutants associated with H2S metabolic and ER stress pathways using physio-biochemical, cellular and molecular techniques. Furthermore, RNA-seq and metabolomics analysis were used to further clarify whether the alleviating effects of H2S pretreatment on hypoxia-induced cell death is regulated by both redox homeostasis and protein-refolding via the unfolded protein response (UPR). The exact mechanism of H2S in improving hypoxia tolerance ability in response to hypoxic stress will be uncovered finally. This project has not only the important scientific significance, but also the potential application in improving the hypoxia tolerance of plants.

硫化氢（H2S）作为一种新型气体信号分子参与动植物细胞的多种生物学过程，并作为O2感受器调控动物细胞低氧胁迫应答反应，但尚无H2S参与植物细胞应答水涝低氧胁迫方面的报道。最近，我们发现外源H2S预处理能够缓解豌豆和玉米根尖细胞死亡，增强拟南芥水涝低氧胁迫耐受性，但其调控机制目前还不清楚。本项目拟以建立了完善水培体系的玉米、拟南芥H2S代谢及ER stress相关突变体为材料，通过生理生化、细胞和分子生物学等技术在不同层次上研究H2S缓解水涝低氧胁迫导致的植物细胞死亡及其与ROS的相互作用，解析H2S调控低氧胁迫诱导的植物根尖细胞ER stress的发生，并通过转录组学及代谢组学分析进一步阐明H2S是否通过调控ROS内平衡以及蛋白的正确折叠进而缓解植物细胞死亡，最终揭示H2S参与水涝低氧胁迫应答、增强植物水涝低氧胁迫耐受性的机制。该项目不仅具有重要的科学意义，同时还具有潜在的实际应用价值。

由于气候变化，水涝灾害在全球范围内频繁发生，严重影响了植物的生长发育，造成农作物的产量大幅度降低。H2S作为一种新型气体信号分子在动植物发育和抵抗逆境胁迫中发挥重要功能，已有研究表明H2S作为O2感受器调控动物细胞的低氧胁迫应答，但是关于H2S参与植物细胞水涝低氧胁迫应答方面的研究还鲜有报道。本项目在建立了拟南芥水淹体系的基础上，通过多种常规及分子生物学方法，对H2S参与植物水涝低氧胁迫的生理功能和分子机制进行了系统的研究。主要研究成果如下：1）外源H2S通过提升细胞抗氧化防御系统、影响H2S的合成与代谢以及低氧应答相关基因的表达增强了植物水涝低氧胁迫的耐受性；2）发现水淹诱导的拟南芥细胞死亡是自噬介导的程序性细胞死亡过程，而H2S主要通过调控自噬减少水淹诱导的细胞死亡；3）H2S作为信号分子协同调节内质网应激诱导的UPR信号通路进而调节拟南芥低氧应答反应；4）转录组学分析揭示外源H2S预处理通过调节低氧应答相关基因PCO1、PCO2、ADH1和HB1以及植物激素ABA和乙烯相关基因的表达，使植物更快地感知和响应低氧环境，进而提高拟南芥对水淹胁迫的耐受能力；5）代谢组学分析证明H2S预处理显著改变了氨基酸的合成与代谢以及植物激素IAA、茉莉酸和水杨酸等代谢物的合成，进而提高了植物水涝低氧胁迫的耐受性；6）蛋白质组学分析表明H2S通过调节信号转导、氨基酸代谢、蛋白质的修复、折叠和降解等途径中相关蛋白质的表达进而增强了拟南芥的水淹耐受性。综上所述，H2S通过增强植物抗氧化能力、调控自噬和UPR信号通路、调节基因转录、蛋白表达和代谢的不同模式或阶段来调控植物细胞对水涝低氧胁迫的应答过程，最终缓解了水淹引起的植物细胞死亡。本研究不仅具有重要的科学意义，同时还为提高农作物的水涝低氧胁迫耐受性提供了理论基础。