State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China; Department of Marine Sciences, University of Connecticut, Groton CT06405, USA.
State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China.
Sci Total Environ. 2021 Apr 1;763:143013. doi: 10.1016/j.scitotenv.2020.143013. Epub 2020 Oct 19.
Harmful algal blooms formed by certain dinoflagellate species often occur when environmental nitrogen nutrients (N) are limited. However, the molecular mechanism by which dinoflagellates adapt to low N environments is poorly understood. In this study, we characterized the transcriptomic responses of Prorocentrum shikokuense to N deficiency, along with its physiological impact. Under N deficiency, P. shikokuense cultures exhibited growth inhibition, a reduction in cell size, and decreases in cellular chlorophyll a and nitrogen contents but an increase in carbon content. Accordingly, gene expression profiles indicated that carbon fixation and catabolism and fatty acid metabolism were enhanced. Transporter genes of nitrate/nitrite, ammonium, urea, and amino acids were significantly upregulated, indicating that P. shikokuense cells invest to enhance the uptake of available dissolved N. Notably, upregulated genes included those involved in endocytosis and phagosomes, evidence that P. shikokuense is a mixotrophic organism that activates phagotrophy to overcome N deficiency. Additionally, vacuolar amino acid transporters, the urea cycle, and urea hydrolysis genes were upregulated, indicating N recycling within the cells under N deficiency. Our study indicates that P. shikokuense copes with N deficiency by economizing nitrogen use and adopting multiple strategies to maximize N acquisition and reuse while maintaining carbon fixation. The remarkable low N adaptability may confer competitive advantages to P. shikokuense for forming harmful blooms in DIN-limited environments.
当环境氮营养物（N）有限时，某些甲藻物种形成的有害藻类水华经常发生。然而，甲藻适应低 N 环境的分子机制还知之甚少。在这项研究中，我们描述了 Prorocentrum shikokuense 对 N 缺乏的转录组反应及其对生理的影响。在 N 缺乏的情况下，P. shikokuense 培养物表现出生长抑制、细胞大小减小、细胞叶绿素 a 和氮含量降低，但碳含量增加。相应地，基因表达谱表明，碳固定和分解代谢以及脂肪酸代谢增强。硝酸盐/亚硝酸盐、铵、尿素和氨基酸的转运体基因显著上调，表明 P. shikokuense 细胞投资以增强对可用溶解 N 的吸收。值得注意的是，上调的基因包括参与内吞作用和吞噬体的基因，这表明 P. shikokuense 是一种混合营养体，它激活吞噬作用以克服 N 缺乏。此外，液泡氨基酸转运体、尿素循环和尿素水解基因上调，表明 N 在 N 缺乏时在细胞内再循环。我们的研究表明，P. shikokuense 通过节约氮的利用并采取多种策略来最大程度地获取和再利用 N 来应对 N 缺乏，同时保持碳固定。这种显著的低 N 适应性可能使 P. shikokuense 在 DIN 受限环境中形成有害水华时具有竞争优势。
