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Increased Ammonium Assimilation Activity in the Scleractinian Coral Pocillopora damicornis but Not Its Symbiont After Acute Heat Stress
Frontiers in Marine Science ( IF 2.8 ) Pub Date : 2020-09-29 , DOI: 10.3389/fmars.2020.565068
Jia Tang , Xingzhen Ni , Jianqing Wen , Lingui Wang , Jian Luo , Zhi Zhou

Ammonium is the main nitrogen resources for scleractinian coral-Symbiodiniaceae symbiotic association, and there is urgent need to investigate the involvement of ammonium assimilation in the heat acclimation of the symbiotic association to heat stress. In the present study, symbiont density and chlorophyll content, as well as redox and ammonium assimilation enzyme activities, in two symbiotic partners of the scleractinian coral Pocillopora damicornis were firstly investigated after acute heat stress (32°C). Symbiont density and chlorophyll content decreased significantly at 24 h (1.81 × 106 cell cm–2, p < 0.05) and 36 h (23.25 pg cell–1, p < 0.05) after heat stress, respectively. We observed significant activity increases of coral nitric oxide synthase, superoxide dismutase and catalase, and symbiont superoxide dismutase after heat stress, but no alterations in the activities of symbiont nitric oxide synthase and catalase during the whole experiment period. The activities of coral glutamine synthetase and glutamine oxoglutarate aminotransferase began to increase significantly at 24 h, and reached the peak at 36 h after heat stress. As for coral glutamate dehydrogenase activity, a significant increase was observed only at 36 h after heat stress. The activities of symbiont glutamine synthetase and glutamine oxoglutarate aminotransferase did not change significantly after heat stress. Secondly, symbiont density, chlorophyll content, apoptosis rate, coral total antioxidant capacity, and caspase3 activation level were determined after glufosinate (glutamine synthetase inhibitor) treatment. Symbiont density decreased significantly at 6 h (1.25 × 106 cell cm–2, p < 0.05) after glufosinate treatment, and symbiont chlorophyll content also decreased significantly during 12–24 h after glufosinate treatment, with the lowest level at 12 h (16.69 pg cell–1, p < 0.05). Furthermore, the coral total antioxidant capacity and caspase3 activation level both increased significantly at 12 h (0.57 U mg–1, 2.08-fold, p < 0.05) after glufosinate treatment, while no significant change was observed for the symbiont apoptosis rate. These results suggest that the ammonium assimilation activity in the coral host P. damicornis, not its symbiont, was induced by acute heat stress, which might contribute to the acclimatization of the symbiotic association to high temperature through regulating coral antioxidant capacity and apoptosis.

中文翻译:

急性热应激后,Scleractinian 珊瑚 Pocillopora damicornis 中氨同化活性增加,但不增加其共生体

铵是石珊瑚-共生科共生协会的主要氮源,迫切需要研究铵同化在共生协会对热应激的热驯化中的参与。在本研究中,在急性热应激 (32°C) 后,首先研究了 scleractinian 珊瑚 Pocillopora damicornis 的两个共生伙伴中的共生体密度和叶绿素含量,以及氧化还原和铵同化酶活性。共生体密度和叶绿素含量分别在热应激后 24 小时(1.81 × 106 细胞 cm-2,p < 0.05)和 36 小时(23.25 pg cell-1,p < 0.05)显着降低。我们观察到热应激后珊瑚一氧化氮合酶、超氧化物歧化酶和过氧化氢酶以及共生体超氧化物歧化酶的活性显着增加,但在整个实验期间共生体一氧化氮合酶和过氧化氢酶的活性没有变化。珊瑚谷氨酰胺合成酶和谷氨酰胺酮戊二酸氨基转移酶的活性在24 h开始显着增加,在热应激后36 h达到峰值。至于珊瑚谷氨酸脱氢酶活性,仅在热应激后 36 小时观察到显着增加。热应激后共生体谷氨酰胺合成酶和谷氨酰胺酮戊二酸氨基转移酶的活性没有显着变化。其次,在草铵膦(谷氨酰胺合成酶抑制剂)处理后测定共生体密度、叶绿素含量、细胞凋亡率、珊瑚总抗氧化能力和 caspase3 活化水平。共生体密度在 6 小时时显着降低(1.25 × 106 细胞 cm-2,p < 0。05) 草铵膦处理后,共生体叶绿素含量也在草铵膦处理后 12-24 小时内显着降低,最低水平为 12 小时(16.69 pg cell-1,p < 0.05)。此外,珊瑚总抗氧化能力和 caspase3 活化水平在草铵膦处理后 12 小时(0.57 U mg-1,2.08 倍,p < 0.05)均显着增加,而共生体细胞凋亡率未观察到显着变化。这些结果表明,珊瑚宿主 P. damicornis 中的铵同化活性,而不是其共生体,是由急性热应激诱导的,这可能通过调节珊瑚抗氧化能力和细胞凋亡促进共生体对高温的适应。草铵膦处理后 12-24 小时内,共生体叶绿素含量也显着下降,最低水平出现在 12 小时(16.69 pg cell-1,p < 0.05)。此外,珊瑚总抗氧化能力和 caspase3 活化水平在草铵膦处理后 12 小时(0.57 U mg-1,2.08 倍,p < 0.05)均显着增加,而共生体细胞凋亡率未观察到显着变化。这些结果表明,珊瑚宿主 P. damicornis 中的铵同化活性,而不是其共生体,是由急性热应激诱导的,这可能通过调节珊瑚抗氧化能力和细胞凋亡促进共生体对高温的适应。草铵膦处理后 12-24 小时内,共生体叶绿素含量也显着降低,最低水平出现在 12 小时(16.69 pg cell-1,p < 0.05)。此外,珊瑚总抗氧化能力和 caspase3 活化水平在草铵膦处理后 12 小时(0.57 U mg-1,2.08 倍,p < 0.05)均显着增加,而共生体细胞凋亡率未观察到显着变化。这些结果表明,珊瑚宿主 P. damicornis 中的铵同化活性,而不是其共生体,是由急性热应激诱导的,这可能通过调节珊瑚抗氧化能力和细胞凋亡促进共生体对高温的适应。草铵膦处理后珊瑚总抗氧化能力和 caspase3 活化水平均在 12 小时后显着增加(0.57 U mg–1,2.08 倍,p < 0.05),而共生体细胞凋亡率未观察到显着变化。这些结果表明,珊瑚宿主 P. damicornis 中的铵同化活性,而不是其共生体,是由急性热应激诱导的,这可能通过调节珊瑚抗氧化能力和细胞凋亡促进共生体对高温的适应。草铵膦处理后珊瑚总抗氧化能力和 caspase3 活化水平均在 12 小时后显着增加(0.57 U mg–1,2.08 倍,p < 0.05),而共生体细胞凋亡率未观察到显着变化。这些结果表明,珊瑚宿主 P. damicornis 中的铵同化活性,而不是其共生体,是由急性热应激诱导的,这可能通过调节珊瑚抗氧化能力和细胞凋亡促进共生体对高温的适应。
更新日期:2020-09-29
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