State Key Laboratory of Marine Environmental Science and College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China; Department of Marine Sciences, University of Connecticut, Groton, CT 06340, USA.
State Key Laboratory of Marine Environmental Science and College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China.
Sci Total Environ. 2021 Jan 20;753:141906. doi: 10.1016/j.scitotenv.2020.141906. Epub 2020 Aug 23.
Symbiodiniaceae are the source of essential coral symbionts of reef building corals. The growth and density of endosymbiotic Symbiodiniaceae within the coral host is dependent on nutrient availability, yet little is known about how Symbiodiniaceae respond to the dynamics of the nutrients, including switch between different chemical forms and changes in abundance. In this study, we investigated physiological, cytometric, and transcriptomic responses in Fugacium kawagutii to nitrogen (N)-nutrient deficiency and different chemical N forms (nitrate and ammonium) in batch culture conditions. We mainly found that ammonium was consumed faster than nitrate when provided separately, and was preferentially utilized over nitrate when both N compounds were supplied at 1:2, 1:1 and 2:1 molarity ratios. Besides, N-deficiency caused decreases in growth, energy production, antioxidative capacity and investment in photosynthate transport but increased energy consumption. Growing on ammonium produced a similar cell yield as nitrate, but with a reduced investment in nutrient transport and assimilation; yet at high concentrations ammonium exhibited inhibitory effects. These findings together have important implications in N-nutrient regulation of coral symbiosis. In addition, we identified ten highly and stably expressed genes as candidate reference genes, which will be potentially useful for gene expression studies in the future.
共生藻是造礁石珊瑚重要共生藻的来源。珊瑚宿主中内共生共生藻的生长和密度取决于营养物质的可利用性，但对于共生藻如何响应营养物质的动态变化，包括不同化学形式之间的转换和丰度的变化，知之甚少。在这项研究中，我们在批量培养条件下研究了 Fugacium kawagutii 对氮（N）营养缺乏和不同化学 N 形式（硝酸盐和铵盐）的生理、细胞计量和转录组响应。我们主要发现，当单独提供时，铵盐的消耗速度快于硝酸盐，而当以 1:2、1:1 和 2:1 摩尔比同时提供两种 N 化合物时，铵盐优先于硝酸盐利用。此外，N 缺乏会导致生长、能量产生、抗氧化能力和光合作用产物运输投资减少，但会增加能量消耗。在铵盐上生长产生的细胞产量与硝酸盐相似，但在营养物质运输和同化方面的投资减少；然而，高浓度的铵盐会表现出抑制作用。这些发现对于珊瑚共生体中 N 营养物质的调控具有重要意义。此外，我们鉴定了十个高度和稳定表达的基因作为候选参考基因，这些基因将来可能对基因表达研究有用。
