海洋硅藻休眠期细胞形成与萌发的硅代谢分子调控机制

Diatom resting stage cells (resting cells and resting spores) is a special way of reproduction and survival strategy in some diatom species to cope with the changes of environmental factors. However, little is known about the active silicon metabolic processes and its regulatory mechanism during the formation and rejuvenation of diatom resting stage cells, especially heavy siliceous mineralization process in diatom resting spores that is different from vegetative cells. In this project, the characteristic and related molecular mechainsms involved in silica uptake and bio-mineralization process of marine diatoms Thalassiosira pseudonana and Chaetoceros mulleri during the formation and rejuvenation of diatom resting stage cells will be investigated based on microscopic observation, physiological and biochemical markers, cell wall proteome analysis, and transcriptomics technology. Meanwhile, silicon metabolism process and related mechanism between resting cells and resting spores during their fomation and rejuvenation, as well as their related differences between resting stage cells and vegetative cells, will also be compared. Furthermore, functional verification of important related genes will be confirmed through gene silencing methods. Finally the biological and the molecular mechanism involved in silicon absorption and bio-mineralization processes during the formation and rejuvenation in diatom resting stages cells will be revealed. This project is expected to give us a new insight into the ecological significance of this special life process of marine diatom as “algal seed bank”. The results will also give us a deeper understanding of diatom survival and competition strategy and its role and the great significance in element biogeochemistry cycling and biological evolution in marine ecosystem.

硅藻休眠期细胞（休眠细胞和休眠孢子）是某些硅藻在生长环境发生变化时的一种特殊的繁殖方式和生存适应。但人们对其休眠期细胞形成与萌发时，活跃的硅代谢过程以及硅藻休眠孢子不同于营养细胞的重硅质化过程及其分子调控机制知之甚少。因此，本项目拟以海洋硅藻假微型海链藻和牟氏角毛藻为研究对象，综合形态学显微观察、生理生化指标、基因表达、细胞壁蛋白质组分析及转录组测序技术，分别研究其休眠细胞和休眠孢子形成与萌发时的硅吸收与生物硅化特征，比较重硅质化休眠孢子和非重硅质化休眠细胞形成与萌发时硅代谢及分子调控的差异，以及它们与营养细胞硅代谢的不同，再采用基因沉默等方法进行重要相关基因的功能验证，最终阐明海洋硅藻休眠期细胞硅吸收和生物硅化特征及其分子调控机制，以及休眠期细胞作为“藻细胞种子库”的生态学意义。该研究结果将有助于深入理解海洋硅藻的生存与竞争策略及其在海洋生态系统物质循环和生物进化中的作用。

硅藻休眠期细胞（休眠细胞和休眠孢子）是某些硅藻在生长环境发生变化时的一种特殊的繁殖方式和生存适应现象。但人们对其休眠期细胞形成与萌发时，活跃的硅代谢过程以及硅藻休眠期细胞不同于营养细胞的重硅质化过程及其分子调控机制知之甚少。因此，本项目以海洋硅藻假微型海链藻（Thalassiosira pseudonana）和牟氏角毛藻（Chaetoceros mulleri）为研究对象，综合显微形态观察、生理生化指标、蛋白质组学、转录组学、基因操作技术、以及生态学分析分别研究了两者休眠期细胞形成与萌发时的硅吸收与生物硅化特征、分子调控机制及其生态学意义。主要结果如下：黑暗低温3月和缺氮缺铁高盐协同30天分别诱导了假微型海链藻休眠细胞和牟氏角毛藻休眠孢子的形成。进行了休眠细胞和休眠孢子形成过程，在细胞壁显微形态结构、生理生化特征、硅吸收与利用、硅化基因表达、及蛋白表达等方面与营养细胞的差异特征研究。分别解析了假微型海链藻休眠细胞与牟氏角毛藻休眠孢子形成过程硅代谢特征及调控机制。进行了假微型海链藻休眠细胞和牟氏角毛藻休眠孢子的萌发实验。两者的休眠期细胞都能在几天内成功萌发。研究了休眠期细胞萌发时的形态、生理变化，解析了牟氏角毛藻休眠孢子萌发过程相关硅代谢基因的表达与调控。运用基因操作技术对2个未知功能的硅化相关基因进行了细胞定位和功能研究，并对硅化相关基因的特有结构域RXL和KXXK的功能进行了进一步解析。结合生态学实验，揭示了假微型海链藻休眠细胞硅代谢调控在其休眠细胞抵御细菌分解、保持细胞存活方面的重要生态学意义。该研究成果加深了对海洋硅藻硅代谢与生物硅化特征的理解，特别是对休眠期细胞的作用，有助于深入揭示硅藻生存与竞争策略，以及硅藻休眠期细胞在硅和碳生物地球化学循环的重要生态学意义。