甲藻赤潮胁迫下大型海藻羊栖菜的光合应答机制研究

The red tide-inhibiting effects of macroalgae (seaweeds) have received much attention, but the allelopathic effects and mechanisms of red tides' on macroalgae got little concern by far. Photosynthetic adaptation is the cornerstone that determines the allelopathic interactions between the macroalga and harmful algae. Furthermore, the harvesting, sexual reproduction and seedling conservation periods of economic seaweed Sargassum fusiforme artificial cultivated in Wenzhou coastal waters coincide with the high incidence periods of red tides (April-August), which allows it to be an ideal material for studying the photosynthesis response mechanism of macrophytes under red tide stresses. . Based on the previous work, this project this project intends to use of Sargassum fusiforme in the coastal waters of Wenzhou as the test object, to infect them with non-toxic Prorocentrum donghaiense and toxic Karenia mikimotoi, respectively. In this process, chlorophyll fluorescence, key enzyme activities of photosynthetic carbon fixation, and sequencing and analysis of transcriptome were performed to analyze energy transfer and cellular resources distribution strategy, molecular mechanism of “light reaction” and “dark reaction” response of Sargassum fusiforme in different life stages, to different type dinoflagellate red tides. On these basses, microscope observation and comparative analysis of the main biochemical components between the tissues of Sargassum fusiforme and those subjected to dinoflagellate red tides, were performed to revealed the histological basis of different types red tide stresses and the negative effects of red tide stresses on the quality of Sargassum fusiforme. The expected results of the proposal also will provide theory fundaments and scientific data for the comprehensive assessment of the negative effects of dinoflagellate red tides on mariculture of Sargassum fusiforme.

大型海藻的赤潮抑制效应备受关注而赤潮对大型海藻的克生作用及机理却没有受到重视。光合适应是决定藻类间克生效应的基石,而温州海域人工栽培羊栖菜的采收期、有性繁育期及幼苗养护期均与该海区的赤潮高发期(4月-8月)重合,是研究赤潮胁迫下大型海藻光合应答机制的理想材料。. 本项目拟在前期工作的基础上,以温州海域人工栽培的羊栖菜为受试对象,分别利用非产毒的东海原甲藻、产毒的米氏凯伦藻对其进行感染。在此过程中,通过叶绿素荧光与光合固碳关键酶活性检测、转录组测序及分析阐明不同生活史阶段羊栖菜的“光反应”和“暗反应”应答特征、生物膜能量及细胞资源分配策略与分子机理。在此基础上, 结合组织学及主生化成分比较揭示不同生活史阶段羊栖菜光合应答不同类型甲藻赤潮胁迫的组织学基础和赤潮胁迫对羊栖菜品质的影响。预期研究结果为准确、客观的评价甲藻赤潮频发对经济海藻羊栖菜栽培的危害提供理论依据和科学依据。

本项目针对近年来沿海海域赤潮频发正引发大型海藻场的快速退化以及养殖经济海藻的损伤而现有研究大多关注大型海藻的赤潮藻抑制效应, 很少关注赤潮藻对大型海藻的危害这一现状，以经济海藻羊栖菜为受试对象, 分别利用产毒的米氏凯伦藻和非产毒的东海原甲藻对其进行感染，在此过程中, 采用叶绿素快速荧光检测、光合作用关键酶活性分析和转录组测序分析等技术手段解析了不同生活史阶段羊栖菜的光合作用应答特征、光合原件受损情况与分子响应。. 结果发现与米氏凯伦藻共培养会显著抑制羊栖菜合子的生长发育、色素合成及光合效率，且抑制程度具有浓度依赖性。在不同感染方式下，其抑制效率从大至小依次为活细胞悬浮液>无细胞上清液>细胞破碎液，表明其主要通过细胞接触和向细胞外分泌化感物质对产生抑制作用。受感染羊栖菜幼苗的转录组学分析显示其光合作用相关元件的基因出现了差异性表达，表明其能够通过对光合作用相关基因表达的上调产生一定的抗性。此外，羊栖菜柱状表皮细胞组成的致密表皮层可能作为保护屏障，增强了其对米氏凯伦藻胁迫效应的耐受能力。. 东海原甲藻对羊栖菜具有和米氏凯伦藻类似的抑制作用作用，通过JIP-test分析发现，其分泌的化感物质会抑制羊栖菜合子PSII的电子传递，使PSII部分光化学反应中心（RCs）失活，进而使大量激发能转化为热能被耗散掉，从而降低了羊栖菜的光合作用效率。在羊栖菜藻体表面分离到一株溶藻效果显著的菌株，并且发现其主要是通过分泌溶藻物质的方式杀藻。此外，羊栖菜养殖提高了养殖区的浮游植物生物量和多样性指数，对海洋环境起到改善作用。. 以上结果为准确、客观的评价甲藻赤潮频发对大型海藻养殖及近岸自然海藻种群的危害提供了理论依据和科学数据。而羊栖菜附着微生物的赤潮藻溶藻功能及大型海藻养殖的生态环境效益研究结果，对于全面评估近岸海藻养殖的赤潮防治作用及除藻剂开发提供了证据和新思路。