陆生橘色藻的碳同化和碳分配行为适应环境干湿交替的生理机制研究

The algae in order Trentepohliales play important ecological functions in terrestrial ecosystem succession and soil formation, and have notable landscape benefits and economic value. Multiple alternating immersion and emersion is the main environmental characteristics in Trentepohliales algae's habitats. How to adapt multiple alternating immersion and emersion are the critical scientific problems in population succession, and resource conservation and utilization of Trentepohliales algae. Based on previous studies, we speculate particular characteristic of carbon assimilation and carbon distribution of Trentepohliales algae might play important role in adapting to alternating immersion and emersion, however, the physiological mechanism of this remains unclear. The present proposal will take Trentepohlia arborum as the study subject and take the typical habitat of Trentepohlia as research site. We plan to monitor annual variation of photosynthesis, cytochemistry and environmental factors through in situ investigation. At meanwhile, we plan to reveal characteristics of T. arborum to utilize different inorganic carbon source via inhibition assay. We also plan to simulate different modes of alternation of immersion and emersion though reciprocal transplants experiments and simulated rainfall experiments based on results of in situ investigation. And subsequently, we will study photosynthetic physiological response and the dynamic allocation of carbon between protein, lipid and carbohydrate responding to alternation of immersion and emersion. The main goal of the present proposal is to clarify the physiological mechanism on regulating carbon assimilation and carbon distribution by alternating immersion and emersion. The accomplishment of this project will enrich our knowledge about water physiological ecology of terrestrial algae, and provide research foundation for application of Trentepohliales algae in near future.

橘色藻(Trentepohliales)在土壤形成和生态系统演替过程中发挥重要生态功能，且具有重要景观和经济价值。多重干湿交替变化是其生境地主要环境特点，如何适应这一特点是影响其自然种群生消变化和资源保护与利用的关键问题。基于前期研究，我们推测橘色藻特殊的碳同化和碳分配行为在其适应环境干湿交替变化中发挥重要作用，但目前对这一适应机制尚不清楚。本项目拟以树栖橘色藻为研究对象，以其典型生境地为研究地点，原位监测其自然生境下的光合作用、生化组分和环境因子的周年变化；通过抑制实验，揭示橘色藻对不同无机碳的利用特性；通过交互移植和模拟降雨，系统研究橘色藻对不同干湿交替的光合作用响应模式和碳在油脂-蛋白质-碳水化合物间的流转规律。通过以上研究，阐明橘色藻碳同化和碳分配行为适应环境干湿交替的生理机制，以期丰富陆生藻水分生理生态学的知识，为科学评估橘色藻种群变化以及在生物技术领域应用提供依据和研究基础。

橘色藻(Trentepohliales)在土壤形成和生态系统演替过程中发挥重要生态功能，且具有重要景观和经济价值。围绕橘色藻对多重干湿交替变化的适应机制这一科学问题，本项目从模式实验藻株的分离、纯化开始，开展野外原位实验采集橘色藻生境地的理化条件，建立了实验室不同供水条件研究平台以模拟野外环境，通过逐步研究橘色藻在不同水分条件下的光合生理特性，橘色藻在不同供水条件下对无机碳源的同化途径，以及橘色藻主要生化组分对水分条件的转变的响应。通过以上研究，我们实验证实了橘色藻在水生状态下的光补偿点、光饱和点和光饱和时光合速率均高于气生状态下的橘色藻，而气生状态下的CO2饱和时最大光合速率要高于在水生状态下的最大光合速率。在水生状态下，橘色藻可以利用溶液中的碳酸氢根进行光合作用。在高DIC环境下橘色藻通过胞外CA和CO2泵协同作用来利用环境中碳酸氢根；而在低DIC环境下，橘色藻除上述途径外还能诱导产生C4途径，在水生状态下可以直接将碳酸氢根与PEP固定，生成的OAA再通过转氨酶催化生成天冬氨酸转运入叶绿体内，从而保证了其在环境中CO2供应不足时也可生长。在由水生向气生状态转变过程中，橘色藻胞内油脂含量降低而总糖含量增加，叶绿素含量减少而类胡萝卜素含量增加，一方面揭示了橘色藻藻华现象的产生并非源于生物量的快速增长，而是由于胞内类胡萝卜素含量的相对提高而显现出红色，另一方面碳从油脂转移至碳水化合物和色素类物质，有利于细胞的质膜保护和对干旱的抗逆能力。研究还发现树栖橘色藻T. arborum HJ和T. arborum LST06)株系表现出优越的联产油脂和类胡萝卜素的能力，以及对高酸环境中铵氮选择性利用的能力。通过以上研究，从碳流转的角度阐明了橘色藻适应环境干湿交替的生理机制，丰富了陆生藻水分生理生态学的知识，为科学评估橘色藻种群变化，以及发掘和推动橘色藻在多领域的应用提供依据和研究基础。