褪黑素调控氧化还原稳态减轻低温胁迫下红树植物秋茄PSI光抑制的机制研究

低温尤其是极端低温是限制中国红树林分布及生长发育的主要因素。秋茄是我国分布最广、最北，且耐寒性最强的红树植物，是红树林耐寒研究的最佳材料。研究证明，褪黑素能显著增强红树林耐寒性，但其抗寒机制仍不清楚。我们前期研究表明，褪黑素是秋茄低温诱导氧化还原稳态重建的关键因素，也是减轻PSI光抑制、增强光合能力的必要条件。在此基础上，本项目利用高效液相色谱串联质谱、qRT-PCR技术等研究低温胁迫下秋茄内源褪黑素合成关键酶活性和基因表达，明确秋茄褪黑素合成途径；通过PTM技术等研究褪黑素对低温胁迫下ROS、RNS形成的蛋白氧化修饰的影响，阐明低温胁迫下褪黑素介导秋茄氧化还原网络的分子过程；采用RNA-Seq等技术鉴定褪黑素调控低温胁迫下PSI电子传递过程中的关键基因，最终阐明褪黑素调控秋茄氧化还原稳态减轻PSI光抑制的分子机制。这些结果为建立红树林抗低温栽培技术奠定重要理论依据，并具有实践应用价值。

Low temperature, especially extreme cold weather events, is a main factor limiting the distribution and growth of mangroves in China. Kandelia obovata is the most cold-tolerant mangrove and is widely distributed in northern of China. It is usually used as a material for clarifying the cold-tolerant mechanisms in mangrove trees. Melatonin is known to enhance the cold tolerance of mangrove, but its regulatory mechanism remains unclear. Our previous studies show that melatonin is a key factor to reconstruct the redox steady-state under low temperature, and it is also essential for reducing PSI photoinhibition and therefore enhancing photosynthetic capacity in K. obovata. Based on the above results, this project will determine the activities of melatonin biosynthesis enzymes and the related gene expression using HPLC-MS-MS and qRT-PCR to identify the low temperature-induced melatonin biosynthesis pathway, investigate how melatonin treatment affects oxidative modification of reactive oxygen species (ROS)- and reactive nitrogen species (RNS)-induced proteins using PTM to clarify melatonin-mediated redox network, and finally identify the key genes involved in PSI electron transfer using RNA-Seq to explore how melatonin-regulating redox homeostasis reduces PSI photoinhibition under low temperature stress. Our results may be useful for the establishment of cold-resistant cultivation in mangrove, and have a practical application of value.