Jiangsu Key Laboratory of Marine Bioresources and Environment/Jiangsu Key Laboratory of Marine Biotechnology, Jiangsu Ocean University, Lianyungang, 222005, China; Co-Innovation Center of Jiangsu Marine Bio-Industry Technology, Jiangsu Ocean University, Lianyungang, 222005, China; State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, Fujian, 361005, China; Department of Marine Sciences, University of Connecticut, Groton, CT, 06340, USA.
Jiangsu Key Laboratory of Marine Bioresources and Environment/Jiangsu Key Laboratory of Marine Biotechnology, Jiangsu Ocean University, Lianyungang, 222005, China; Co-Innovation Center of Jiangsu Marine Bio-Industry Technology, Jiangsu Ocean University, Lianyungang, 222005, China.
Harmful Algae. 2020 Feb;92:101770. doi: 10.1016/j.hal.2020.101770. Epub 2020 Feb 12.
Nitrogen (N) is an essential nutrient for phytoplankton growth. There is ample evidence that N enrichment promotes harmful algae blooms (HABs) but molecular mechanisms regulating N-nutrient uptake and metabolism are not so clear, especially for the raphidophyte Heterosigma akashiwo, which forms ichthyotoxic HABs in many coastal waters. In this study, the utilization of three different chemical forms of N (nitrate, ammonium, and urea) by H. akashiwo CCMA 369 was investigated in batch culture conditions. Results showed that H. akashiwo grew well on all three N compounds, and the highest cell yield occurred in the NH culture group. Reverse transcription quantitative PCR analysis revealed that the expression of high-affinity NO transporter (NIT), NH transporter (AMT) and high-affinity urea active transporter (DUR3), were significantly up-regulated under N-limitation compared to the N-replete control. The mRNA levels of AMT and DUR3 also displayed a clear diel rhythm, with high levels at midnight. In addition, NH addition (5 μM) did not depress the transcript abundance of any of the three N transporters. Compared with the co-occurring immobile diatom Skeletonema costatum, the high expression of AMT in dark period in H. akashiwo is consistent with its diel vertical migration behavior, which may promote N-nutrient acquisition from deeper layers and give advantages for H. akashiwo to form blooms.
氮（N）是浮游植物生长的必需养分。有充分的证据表明，N 富集会促进有害藻类大量繁殖（HABs），但调节 N 营养吸收和代谢的分子机制尚不清楚，特别是对于形成鱼毒性赤潮的赤潮藻 Heterosigma akashiwo。在本研究中，在分批培养条件下研究了 H. akashiwo CCMA 369 对三种不同化学形式的 N（硝酸盐、铵盐和尿素）的利用。结果表明，H. akashiwo 在所有三种 N 化合物上都生长良好，NH 培养组的细胞产量最高。反转录定量 PCR 分析显示，与 N 充足的对照相比，在 N 限制下，高亲和力 NO 转运体（NIT）、NH 转运体（AMT）和高亲和力尿素主动转运体（DUR3）的表达显著上调。AMT 和 DUR3 的 mRNA 水平也显示出明显的昼夜节律，午夜时水平最高。此外，NH 加（5 μM）并没有抑制三种 N 转运体的转录丰度。与共存的不运动硅藻 Skeletonema costatum 相比，H. akashiwo 在暗期 AMT 的高表达与其昼夜垂直迁移行为一致，这可能促进了从更深层获取 N 营养，并使 H. akashiwo 形成赤潮的优势。
