海洋酸化对塔玛亚历山大藻产毒的影响及分子机理研究

With the rising atmospheric CO2 levels at the unprecedented rate, ocean acidification is considered as a major threat to marine ecosystems. Phytoplankton, the main primary producer of the marine ecosystem, is found to be sensitive to ocean acidification. Previous research indicated that microalgae of harmful algal species (HAS), as an important component in phytoplankton community, are more sensitive to this kind of environmental change. Some HAS even changed their toxin profiles with elevated ocean acidification, whereas little is known about the underlying mechanism. In this project, we propose to investigate the impact of elevated pCO2 on toxin production of an Alexandrium tamarense strain isolated from the East China Sea. The differential PST toxin synthesis under elevated pCO2 treatments of A. tamarense will be compared at cellular, protein and gene levels. The major key factors regulating the toxin production under ocean acidification will then be selected using the RNA-Seq technology, and the response of these factors in transcription and translation levels will also be analyzed. Consequently, it will be discussed about the molecular basis of influences from ocean acidification on PST synthesis of A. tamarense. This study is going to provide the reference data assisting evaluation of toxicity level of HAS under ocean acidification.

随着大气CO2浓度升高，海洋酸化日益加剧，对海洋生态系统的影响备受关注。海洋浮游植物作为海洋初级生产力的主要贡献者，生理生化过程易受海洋酸化影响。赤潮藻类作为海洋浮游植物的重要类群之一，对海洋酸化更为敏感，其中，有毒赤潮藻类的产毒特征也发生相应变化，但是目前海洋酸化对有毒赤潮藻产毒方面的影响研究较少。本项目拟以我国东海产麻痹性贝毒PSTs的塔玛亚历山大藻作为对象，研究海洋酸化影响下该藻的产毒特征变化；并利用RNA-Seq技术筛选酸化影响下PSTs毒素合成的主要调控基因，分析其在转录水平和翻译水平的表达规律，探讨海洋酸化影响塔玛亚历山大藻PSTs毒素合成的分子机理，进而从细胞、基因及蛋白等多个水平阐释海洋酸化对塔玛亚历山大藻产毒的影响。本项目将丰富赤潮生态学研究，并为评价海洋酸化影响下有毒赤潮的危害及风险等级提供参考数据。

近几十年来，赤潮在我国近海频发，其中有毒赤潮不论频率还是规模，都有扩大的趋势，研究者认为这可能是与大气CO2浓度升高引发的海洋酸化一系列变化有关。海洋环境的酸化以及大气CO2的溶解，能使有毒浮游植物生长、代谢和产毒发生变化，进而通过食物链对人类造成影响。本项目研究了大气CO2加富条件下，产毒塔玛亚历山大藻东海株的生长和产毒情况，结果表明，大气CO2浓度的升高，能显著促进实验藻种的生长速率，和对数生长期的光合作用效率，而分析实验藻株所产麻痹性贝毒各组分：C1、C2、GTX1、GTX2、GTX3、GTX4、GTX5、STX、dcGTX2、dcGTX3、和dcSTX发现，毒素C1、C2、GTX2、GTX3、GTX5、STX、dcGTX2、dcGTX3、dcSTX产量有所减少，但是GTX1，GTX4产量明显增加，这两种毒素产量的增加使得藻细胞的毒性增强约75%，可见，大气CO2浓度的升高能显著增强产毒塔玛亚历山大藻东海株的生长和毒性。通过转录组分析不同CO2浓度下实验藻种的差异表达基因，筛选出大分子合成相关基因GO:0009059 和 GO:0034645，并发现CO2的升高确实能刺激该关键基因的表达，即大气CO2的升高确实能影响塔玛亚历山大藻大分子化合物的合成。