中国南海已知的珊瑚礁种类多达 571 种，与珊瑚大三角区数目相当。在过去的十五年间，由于全球气候变化和过度的海洋开发，南海珊瑚覆盖率由高于 60%下降至不到 20%。珊瑚白化现象日益严重，对珊瑚礁生态系统产生了严重威胁。珊瑚与虫黄藻的功能性共生是珊瑚礁生态系统中最重要的基础。虫黄藻捕获二氧化碳、合成有机质，在地球碳循环过程中扮演着重要的角色，同时为宿主珊瑚和“海底热带雨林”的生物多样性提供最基础的能量来源。但虫黄藻与珊瑚之间的代谢补偿机制以及其在珊瑚共生体形成和白化过程中的作用尚未完全明确。

          There are 571 known species of coral reefs in the South China Sea, which is comparable to the number of coral triangles. Over the past 15 years, the coverage rate of coral in the South China Sea has declined from above 60% to less than 20% due to global climate change and excessive marine development. Currently, coral bleaching is becoming increasingly serious and poses a serious threat to coral reef ecosystems. The functional symbiosis between corals and zooxanthellae is the most important foundation of coral reef ecosystem in that the algae play an important role in the Earth’s carbon cycle by capturing carbon dioxide and synthesizing organic matter and they also provide the most fundamental source of energy for the host corals and the biodiversity of the “submarine rainforest”. However, the mechanism of metabolic compensation between corals and zooxanthellae and its role in the formation of coral symbiosis and bleaching process are not fully clear.

近日，海南大学南海海洋资源利用国家重点实验室、海洋学院环境微生物团队，以南海广布珊瑚虫纲紫点海葵（Heteractis crispa）为模式，研究了虫黄藻与宿主的甾醇组成结构特征以及甾醇稳态与白化之间的关系。发现甾醇的动态调控，特别是胆固醇含量的降低可能是导致海葵白化的重要原因之一。同时，项目组首次重建了虫黄藻甾醇生物合成通路；并从分子和代谢物水平上，明确了虫黄藻甾醇合成的环境变化适应性特征。理解虫黄藻和珊瑚之间的复杂关系或有望帮助理解珊瑚白化机制，同时可能帮助拓展对共生生命体系协同进化机制起源、进化和多样性的认知，并为化学生物学手段改良珊瑚抗逆性状、提高珊瑚繁育成活率和减缓珊瑚白化提供理论依据。

          Recently, the Environmental Microbiology Team from MRU and the School of Ocean of Hainan University studied the structural characteristics of sterol composition of zooxanthellae and their hosts as well as the relationship between sterol homeostasis and bleaching with the Heteractis crispa as a model which belongs to the widespread actinozoa in the South China Sea. It was found that the dynamic regulation of sterol, especially the reduction of cholesterol content, may be one of the important causes of Heteractis crispa bleaching. Meanwhile, the team reconstructed the sterol biosynthesis pathway of zooxanthellae for the first time and clarified the adaptive characteristics of environmental changes of sterol synthesis in zooxanthellae at the molecular and metabolite levels. Understanding the complex relationship between zooxanthellae and corals may be helpful to understand the mechanism of coral bleaching and may also be helpful to expand the knowledge of the origin, evolution and diversity of co-evolutionary mechanisms of endosymbiont systems, and it can provide a theoretical basis for chemical biological means to improve the resistance traits of corals, improve the survival rate of coral reproduction and slow down coral bleaching.

图. 高温（HT）和甾体饥饿（ITA）引发的紫点海葵白化对比

相关成果发表于微生物学权威刊物《mSystems》。该研究获得了自然资源部、海南省科技厅、海南大学等项目的支持，由南海海洋资源利用国家重点实验室、海洋学院路延笃教授联合生态与环境学院赵洪伟副教授等完成。

         The related result was published in mSystems, an authoritative journal of microbiology. The research was supported by the projects of Natural Science Foundation of China, the Department of Science and Technology of Hainan Province and Hainan University. And it was completed by Professor Lu Yandu from MRU and School of Ocean of Hainan University and Associate Professor Zhao Hongwei from College of Ecology and Environment.

　文章链接：https://msystems.asm.org/content/5/5/e00765-20

         Link to full text: https://msystems.asm.org/content/5/5/e00765-20