氮磷限制条件下球形棕囊藻生理生化响应及转录组学研究

Study on Physiological and Biochemical Response and Transcriptomics of Phaeocystis globosa Under N- or P-limitation

关键词:  球形棕囊藻  氮磷限制  生理生化  转录组

Key words:  Phaeocystis globosa  N- or P-limitation  physiology and biochemistry  transcriptome

摘要:

氮磷营养限制对球形棕囊藻(Phaeocystis globosa)生长能够产生显著的抑制作用,但其内在作用机理仍不清晰。为从细胞生理生化及转录组层面全面解析球形棕囊藻在氮磷限制下的响应机制,本实验设置氮限制组(N:P=4:1)、磷限制组(N:P=64:1)与对照组(N:P=16:1),测定其生理生化指标并结合转录组学分析,通过比对得到差异表达unigene 14 272个,其中氮限制组上调基因4 397个,下调基因3 679个；磷限制组上调基因4 963个,下调基因5 079个。结果表明氮限制对球形棕囊藻光合作用抑制效果最显著,且细胞由结构型多糖合成向储能代谢型糖类物质合成转变；磷限制条件下,部分光反应蛋白合成基因上调,细胞增殖被显著抑制,囊体更薄,细胞内糖胺聚糖及脂肪酸合成相关基因均上调表达。此外,氮磷限制均会提高细胞转运蛋白的表达,并抑制蛋白酶体的合成。结果认为球形棕囊藻代谢活动受氮限制影响较大,生长增殖及囊体强度受磷限制影响更大。本研究从表观及分子层面初步阐释了球形棕囊藻在氮磷限制下的响应机制,为进一步揭示其生理代谢及成囊过程的内在机理提供参考,同时为相关部门制定有害藻华防治策略提供依据。

Abstract:

Nitrogen or phosphorus nutrient limitation can significantly inhibit the growth of Phaeocystis globosa, but its internal mechanism is still unclear. In order to comprehensively analyze the response mechanism of P.globosa under N- or P-limitation from the aspects of cell physiology, biochemistry and transcriptome, we set up N-limitation group (N:P=4:1), P-limitation group (N:P= 64:1) and control group (N:P=16:1) in this experiment. The physiological and biochemical indexes were determined and combined with transcriptome analysis. Through comparison, 14 272 differentially expressed unigenes were obtained, including 4 397 up-regulated genes and 3 679 down-regulated genes in the N-limitation group. In the P-limitation group, 4 963 genes were up-regulated and 5 079 genes were down-regulated. The results showed that N-limitation had the most significant inhibitory effect on photosynthesis of P.globosa, and the cells changed from structural polysaccharide synthesis to energy storage metabolic carbohydrate synthesis. Under the condition of P-limitation, some genes related to photosynthesis protein synthesis were up-regulated, cell proliferation was significantly inhibited, colonies were more fragile, and genes related to glycosaminoglycan and fatty acid synthesis in cells were up-regulated. In addition, N- or P-limitation can increase the expression of cell transporters and inhibit the synthesis of proteasome. The results showed that the metabolic activity of P.globosa was greatly affected by N-limitation, and the growth, proliferation and colony strength of P.globosa were more affected by P-limitation. In this study, the response mechanism of P.globosa under N- or P-limitation was preliminarily explained from the apparent and molecular levels, which provided a reference for further revealing the internal mechanism of its physiological metabolism and colony formation process, and provided a basis for relevant departments to formulate prevention and treatment strategies for algal bloom.