Hainan Aquaculture Breeding Engineering Research Center, College of Marine Sciences, Hainan University, Haikou, Hainan, 570228, China.
Department of Marine Sciences, University of Connecticut, Groton, Connecticut, 06340, USA.
J Phycol. 2021 Aug;57(4):1187-1198. doi: 10.1111/jpy.13156. Epub 2021 May 8.
The physiological response of symbiotic Symbiodiniaceae to high temperature is believed to result in coral bleaching. However, the potential effect of nitrogen availability on heat acclimatization of symbiotic Symbiodiniaceae is still unclear. In this study, physiological responses of Symbiodiniaceae Cladocopium goreaui to temperature and nitrogen nutrient stress conditions were investigated. Nitrogen deficiency caused significant declines in cell concentration and chlorophyll content per cell, but significant increases in nitric oxide synthase activity, caspase3 activation level, and cellular carbon content of C. goreaui at normal temperature. Algal cells under high temperature and nitrogen deficiency showed significant rises in Fv/Fm, catalase activity, and caspase3 activation level, but no significant changes in cell yield, cell size, chlorophyll content, superoxide dismutase, nitric oxide synthase activity, and cellular contents of nitrogen and carbon, in comparison with those under normal temperature and nitrogen deficiency. Growth, chlorophyll, and nitrogen contents of algal cells under the high temperature and nitrogen-replete conditions were significantly higher than those under high temperature or nitrogen deficiency alone, whereas nitric oxide synthase activity, superoxide dismutase activity, catalase activity, carbon content, and caspase3 activation level exhibited opposite trends of variation. Transcriptomic and network analyses revealed ion transport and metabolic processes mainly involved in regulating these physiological activities under different temperature and nitrogen nutrient. The totality of results shows that high temperature activates stress responses, induces antioxidant capacity of apoptosis, and limits the growth rate of C. goreaui. Adequate nitrogen nutrient can improve the resilience of this Symbiodiniaceae against heat stress through repressed apoptosis, promoted ion transport, and optimized metabolism.
共生虫黄藻对高温的生理反应被认为会导致珊瑚白化。然而，氮素供应对共生虫黄藻热适应的潜在影响尚不清楚。本研究调查了虫黄藻 Cladocopium goreaui 对温度和氮营养胁迫条件的生理反应。氮缺乏导致细胞浓度和每个细胞的叶绿素含量显著下降，但在常温下，一氧化氮合酶活性、caspase3 激活水平和细胞碳含量显著增加。在高温和氮缺乏条件下，藻类细胞的 Fv/Fm、过氧化氢酶活性和 caspase3 激活水平显著升高，但细胞产量、细胞大小、叶绿素含量、超氧化物歧化酶、一氧化氮合酶活性和氮、碳细胞含量无显著变化与常温下氮缺乏相比。在高温和氮充足条件下，藻类细胞的生长、叶绿素和氮含量明显高于高温或氮缺乏单独作用的条件，而一氧化氮合酶活性、超氧化物歧化酶活性、过氧化氢酶活性、碳含量和 caspase3 激活水平则呈现出相反的变化趋势。转录组和网络分析表明，离子转运和代谢过程主要参与调节不同温度和氮营养条件下的这些生理活动。总的结果表明，高温激活应激反应，诱导细胞凋亡的抗氧化能力，并限制 C. goreaui 的生长速度。充足的氮营养可以通过抑制细胞凋亡、促进离子转运和优化代谢来提高这种共生虫黄藻对热应激的恢复力。
