State Key Laboratory of Marine Environmental Science/College of the Environment and Ecology, Xiamen University, Xiamen 361102, China.
State Key Laboratory of Marine Environmental Science/College of the Environment and Ecology, Xiamen University, Xiamen 361102, China; Key Laboratory of Marine Ecology & Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China.
Sci Total Environ. 2020 Jun 1;719:137454. doi: 10.1016/j.scitotenv.2020.137454. Epub 2020 Feb 20.
Phaeocystis globosa is a major causative agent of harmful algal blooms in the global ocean, featuring a complex polymorphic life cycle alternating between free-living solitary cells and colonial cells. Colony is the dominant morphotype during P. globosa bloom. However, the underlying mechanism of colony formation is poorly understood. Here, we comprehensively compared global transcriptomes of P. globosa cells at four distinctive colony formation stages: free-living solitary cells, two cell-, four cell- and multi-cell colonies, under low (20 °C) and high (32 °C) temperatures, and characterized the genes involved in colony formation. Glycosaminoglycan (GAG) synthesis was enhanced while its degradation was decreased during colony formation, resulting in the accumulation of GAGs that are an essential substrate of the colony matrix. Nitrogen metabolism and glutamine synthesis were remarkably increased in the colonial cells, which provided precursors for GAG synthesis. Furthermore, cell defense and motility were down-regulated in the colonial cells, thereby conserving energy for GAG synthesis. Notably, high temperature led to decreased synthesis and increased degradation of GAGs, resulting in insufficient substrates to form the colony. Our study indicates that GAGs accumulation is critical for colony formation of P. globosa, but high temperature inhibits GAGs' accumulation and colony formation.
微囊藻是全球海洋中有害藻类大量繁殖的主要原因，具有自由生活的单细胞和群体细胞之间复杂的多态生命周期。在微囊藻大量繁殖期间，群体是主要的形态类型。然而，群体形成的潜在机制尚未完全理解。在这里，我们综合比较了在低（20°C）和高（32°C）温度下处于四个不同群体形成阶段（自由生活的单细胞、两个细胞、四个细胞和多细胞群体）的微囊藻细胞的全球转录组，并描述了参与群体形成的基因。在群体形成过程中，糖胺聚糖（GAG）的合成增强，而其降解减少，导致 GAG 积累，GAG 是群体基质的重要基质。在群体细胞中，氮代谢和谷氨酰胺合成显著增加，为 GAG 合成提供了前体。此外，在群体细胞中，细胞防御和运动能力下调，从而为 GAG 合成节省了能量。值得注意的是，高温导致 GAG 的合成减少和降解增加，从而导致形成群体的基质不足。我们的研究表明，GAG 的积累对微囊藻的群体形成至关重要，但高温抑制了 GAG 的积累和群体形成。
