氮限制下链状亚历山大藻DMSP合成与生理变化的研究

Studies on the Synthesis of Dimethylsulfoniopropionate and Physiological Variations of Alexandrium catenella(Dinoflagellate) Under Nitrogen Restriction

DMSP是一种重要的生源有机硫化物,甲藻不仅是海洋浮游植物的重要组成部分,同时也是DMSP的重要生产者,但有关DMSP在甲藻中功能的研究比较匮乏。本文首次在链状亚历山大藻中检测到DMSP产生,研究了氮限制对藻细胞生长、细胞体积、活性氧、光合作用能力和DMSP浓度的影响。结果发现,氮限制能引起细胞生长限制及藻细胞DMSP浓度的显著增加。相关性分析发现,细胞活性氧水平和DMSP浓度之间具有强相关关系(Pearson相关系数=0.83),结合实验室之前氮限制下细胞氧化胁迫状态的结果,提示DMSP在藻细胞中具有抗氧化的作用。另外,氮限制下藻细胞体积的显著增大,光合活性降低,提示DMSP在链状亚历山大藻中可能具有渗透压调节的作用。我们的观察进一步验证了前人的发现。本研究还首次分析了链状亚历山大藻中与DMSP合成相关的基因,结果发现,cad-1和cad-2基因可能都参与了DMSP的合成,但发挥不同的作用。实验结果为在甲藻中深入研究DMSP的功能奠定一定的基础,也为揭示甲藻中DMSP合成相关途径提供参考。

Dimethylsulfoniopropionate(DMSP)is a significant biogenic sulfonium compound.Dinoflagellates are important component of phytoplankton and also the active producers of DMSP,however,the studies as for the functions of DMSP in dinoflagellates are limited.In this study,the production of DMSP by this species was firstly reported and the changes of cell growth,cell volume,reactive oxygen species(ROS)production,photosynthesis ability and DMSP concentration were investigated under nitrogen limited condition.The results showed that the growth of the cells were restricted and DMSP concentration were increased significantly under nitrogen limitation condition.Bivariate correlation analysis indicated that there was strong correlation between ROS level and DMSP concentration(Pearson correlation r=0.83,P<0.05).Combined with the studies by our lab previously which indicated a condition of oxidation stress under nitrogen limitation,it was suggested that DMSP may play a role as an antioxidant to balance the excess ROS.In addition,the cell volume increased significantly and photosynthesis ability decreased under nitrogen limitation,which suggested that DMSP may act as an osmolyte in A.catenella when nitrogen was deficient.Previous findings about the functions of DMSP were further confirmed by results of this study.The expression of two related genes probably involved in DMSP biosynthesis were investigated by quantitative real-time PCR.The results suggested that both cad-1 and cad-2 gene may involve in DMSP biosynthesis in A.catenella,however,play different role.This study may be as a reference for the studies of DMSP functions and molecular DMSP biosynthesis pathway.