光温条件对浒苔生长和孢子形成过程的影响及其机理研究

The Ulva bloomed in the northern coast of China every summer, and damaged the coastal ecological environment seriously. Ulva bloom is due to their rapid propagation, and spore formation is the biological basis for their bloom, but because of the bloom process mainly in the sea area, the algal occurrence and disappearance law remained to be studied. Ningbo Ulva prolifera is the same specie as that in North China, which only blooms in the beach, and is convenient for sampling and studying. The main environmental factors for the outbreak of Ulva bloom are the temperature and light, and what are the effects and mechanisms of the temperature and light on the algal growth and spore formation and release? This project aims to solve the above scientific problems and the main contents include: (1) The field monitoring of the natural growth and spore biomass of U. prolifera and analysis of their relationship with environmental factors; (2) Experimental study on the effects of light and temperature conditions on the growth and spore formation of U. prolifera and their metabolites generation; (3) To study the oxidant mechanism of light and temperature stimulation on the spores formation of U. prolifera; (4) To study the phytohormone response and mechanism of light and temperature stimulation on the spore formation of U. prolifera. This study will clarify the suitable light and temperature conditions for the growth and spore formation of Ningbo U.prolifera, clarify the regulation mechanism of light and temperature conditions on the formation of spores, and will contribute to clarify the environmental factors on the occurrence and disappearance law of Ulva bloom.

浒苔绿潮每年夏季在我国北方沿海爆发，严重破坏了海洋生态环境。浒苔能快速繁殖，大量放散的孢子是其快速繁殖的物质基础，但由于浒苔增殖过程主要在海区，对浒苔孢子形成规律还有待研究。与北方浒苔同属于一个种的宁波浒苔（Ulva prolifera），只在沿海滩涂爆发，便于研究其生消规律。浒苔繁殖和爆发的主要环境因素是温度和光照，其影响浒苔生长和孢子发生的规律和作用机理还不是很清楚。本项目针对这个问题，主要开展以下工作：（1）野外监测和分析宁波浒苔自然生长和消亡过程水体孢子量及其与环境因子的关系；（2）实验研究光温条件对浒苔生长、孢子形成及其基因和代谢产物的影响；（3）光温条件刺激浒苔孢子形成的氧化胁迫机理；（4）光温条件刺激浒苔孢子形成的植物激素响应规律和机理。本工作将阐明宁波浒苔生长和孢子形成过程的光温条件，揭示抗氧化系统和植物激素对浒苔孢子形成的调控机理，为浒苔繁殖和生消控制提供参考。

大型绿藻浒苔繁殖迅速，在我国北方频繁引发绿潮灾害。但是宁波浒苔味道鲜美，除了自销还可出口创汇，供不应求。因此，本项目以宁波浒苔为研究对象，探讨光照温度等环境因素对浒苔生长繁殖发育的影响规律及其机理。本研究取得的主要结果：(1) 相比于光周期，暗周期更能促进浒苔生长。而在光周期中，高光（400μmol.m-2.s-1）可以显著促进浒苔生长，并且适当高光强可以抵消高温对浒苔生长的抑制作用。昼夜温差（22-16℃）比22℃恒温更能促进浒苔生长（增幅可达60%），且受高光强的促进。（2）光暗周期、光强和温度对浒苔孢子释放具有交互效应。12L:12D、400μmol.m-2.s-1和25°C是浒苔孢子释放的最适条件。温度和光强对浒苔孢子释放的交互作用较明显，15°C和25°C条件下光强增加均可促进孢子释放，但在30°C下，适中的光强利于孢子释放。（3）转录组结果揭示了浒苔孢子形成机制。在浒苔孢子形成期rETRmax 和Fv'/Fm'最高，光合色素含量增加；孢子形成前期差异基因主要为光合作用、萜类骨架等，中期集中在DNA合成以及激酶等，而后期则以激素信号转导和蛋白合成为主。CL1966.Contig2_mix12、PTOX基因和C3H家族基因可能在孢子形成过程中发挥了关键作用。（4）氧化应激和剪切在孢子形成中发挥了关键作用。在孢子形成过程中，超氧阴离子（O2-）显著增加，抗氧化酶（POD、APX和GR）活性增加，藻体总抗氧化能力增强。剪切可以诱导浒苔在48小时内快速放散孢子，是非剪切对照组的4.67倍。（5）植物激素在浒苔繁殖过程中发挥了调控作用。在浒苔孢子形成过程中，ACC、iPR、tZR和cZR含量显著增加。在逆境条件下，脱落酸和细胞分裂素能够促进浒苔孢子形成。本项目共发表论文9篇，培养研究生5名。该研究阐明了浒苔生长和孢子放散的光温环境因素，为阐明浒苔快速生长机理提供了重要信息。