微藻对极端环境的适应机制及其抗逆性和生态适应进化关系

In our previous studies, microalgal strains from various extreme habitats showed similar biological responses to diurnal temperature fluctuation while they exhibited distinct responses to high light. These phenomena indicate microalgae originated from different habitats develop complicated and diverse stressed-resistant and adaptive strategies to adverse environments. However, the underlying adaptive and regulation molecular mechanisms and their phylogenetic relationships have not been specified. In this project, the adaptive mechanisms of microalgal strains from polar, desert and temperate regions are studied. Transcriptomics, metabolomics and lipidomics will be integrated to explore the intracellular genetic and metabolic regulation networks in adaptation to stressed conditions. The differences and similarities of the adaptive mechanisms will be studied by comparative genomics, then stress-resistance genes with similar functions will be screened, and their phylogenetic relationships will be further analyzed to reveal the functional evolution of stress-resistance genes during the long evolution process. Finally, the fundamental stress-resistant and adaptive mechanisms of microalgae in response to extreme environment, and the corresponding phylogenetic relationships between different algal strains from various habitats will be illustrated. The results of this research may provide a theoretical data for understanding the unique adaptive mechanisms of microalgae to extreme environment, and provide technical supports for exploring microalgae bioresources from extreme environment, especially exploring unique stress-tolerant gene resources from microalgae for genetic improvement on industrial algal strains.

我们前期工作发现，来自不同极端环境的微藻对温度剧烈波动的响应相似，但是对强光胁迫的响应却存在较大差异。可见，基于对极端生存环境的长期适应，源于不同地域的微藻对极端环境的抗逆和适应机制复杂多样。然而目前微藻对极端环境适应和调控的分子机制，尤其是相关代谢途径的进化关系尚未不十分明确。本项目以从极地、沙漠和温带分离、且遗传背景相近的微藻为材料，通过转录组、代谢组和脂组学整合分析，解析逆境下微藻基因表达及代谢网络调控机制；在极地、沙漠和温带大尺度下比较不同地域微藻适应逆境胁迫机制的异同，筛选功能相近的抗逆基因，并对其进化关系进行分析，揭示抗逆基因在进化过程中的功能演变，最终阐明不同极端环境中微藻关键抗逆和适应的分子机制及其进化关系。研究结果将为阐明极端环境生物适应逆境的特殊抗逆机理提供数据资料，同时为极端环境微藻生物资源的开发与应用，尤其是发掘特殊基因资源进行经济微藻遗传育种改良提供技术支持。

来源于极地和沙漠等极端环境的微藻在长期适应与进化过程中形成了独特的适应机制，但其具体涉及的代谢通路和调控机制并不明确。本项目探讨了不同地域的2株小球藻和1株沙漠链带藻对温度、光照等环境因素及其交互作用的生理生态适应机制，运用组学技术初步阐明微藻适应环境胁迫的关键代谢途径与调控机制：（1）比较北极和温带小球藻对温度和强光交互作用的响应，发现北极小球藻比温带小球藻更耐受低温强光胁迫。转录组分析发现其应对低温强光的代谢通路响应涉及光合作用及其下游的碳分配和能量代谢。低温驯化可能通过激活北极小球藻的光保护机制来的抵御过度光激发，同时赋予其对强光逆境的耐受性。（2）对温度逆境下的北极小球藻进行转录组和蛋白组关联分析，发现在转录和蛋白水平KEGG富集的差异代谢通路不完全一致，共同的差异响应通路为光合作用和能量代谢。鉴定到代谢通路中差异蛋白数量比差异基因少。关键基因或蛋白的转录水平与蛋白水平的表达趋势并不一致，关联性较低。（3）基于比较转录组分析阐明了沙漠链带藻突变株（Desmudesmus sp. G3）抵抗强光胁迫的机制。强光下G3可能通过增强光捕获能力，并激活基于捕光天线色素的非光化学淬灭和状态转变，保护PSII免受光损伤，从而维持较高的光化学效率和快速生长。（4）采用PacBio 全长三代转录组技术对北极和温带小球藻进行测序，获得2株小株藻转录本的全长序列，为进一步进行抗逆基因序列进化分析提供重要数据支撑。在应用方面探讨了温度和CO2浓度，强光和氮浓度等环境因素交互作用对北极和沙漠微藻生长和脂质积累的影响，优化了北极小球藻和沙漠链带藻的生物量和脂质积累条件。研究成果为阐明极端环境生物适应逆境的特殊抗逆机理提供数据资料，同时为极端环境微藻生物资源的开发与高密度培养提供技术支持。项目共发表论文8篇，其中SCI论文7篇，获得科技奖励1项。