State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing, 210023, PR China.
Suzhou Vegetable Research Institute, Jiangsu, Suzhou, 215008, PR China.
Toxicon. 2021 Jan 30;190:50-57. doi: 10.1016/j.toxicon.2020.12.008. Epub 2020 Dec 16.
Lake Taihu is the third largest freshwater lake located in eastern China. In recent years, it has experienced extensive cyanobacterial (Microcystis spp.) blooms that produce toxic microcystins (MCs), which may have acute and chronic hepatotoxic effects in animals and humans. Although the impact of MCs on both terrestrial and aquatic plants is well documented, the effects and underlying mechanisms of the harmful toxin MC-LR on Euryale ferox Salisb seedlings have rarely been reported. Thus, herein, the antioxidant response mechanisms and the biosynthesis of secondary metabolites during the exposure of E. ferox Salisb seedlings to varying MC-LR concentrations (0.05, 0.2, 1, and 5 μg/L) were thoroughly investigated after exposure periods (7, 14, 21 d). Our study revealed that the seedling growth was inhibited with increasing MC-LR exposure concentration that significantly induced at 1 μg/L and reached a maximum level at 5 μg/L, whereas the activity of the antioxidant enzymes catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD) in the seedling cells increased gradually with increasing MC-LR concentration and longer exposure time. The maximum malondialdehyde (MDA) content was 4.3-fold higher than that of the control group under an MC-LR concentration of 5.0 μg/L after 7 days of exposure treatment. The study of the seedling detoxification mechanism revealed that the content of total glutathione (tGSH) and reduced glutathione (GSH), as well as the activities of GSH sparse transferase (GST) and glutathione reductase (GR), increased to varying degrees and reached a maximum level at 1 μg/L. Therefore, the exposure to MC-LR can promote the accumulation of secondary metabolites and increase the activities of secondary metabolic enzymes in the seedlings. Further investigation of these antioxidative mechanisms will provide additional information for the identification and development of bio-indicators to evaluate the environmental impact of MCs on aquatic ecosystems.
太湖是中国东部第三大淡水湖。近年来，它经历了广泛的蓝藻（微囊藻属）水华，产生有毒的微囊藻毒素（MCs），这些毒素可能对动物和人类具有急性和慢性肝毒性作用。尽管 MCs 对陆地和水生植物的影响已有充分记录，但 MC-LR 对芡种子苗的有害毒素的影响和潜在机制却很少有报道。因此，在此，在暴露于不同 MC-LR 浓度（0.05、0.2、1 和 5μg/L）后，彻底研究了芡种子苗暴露于 MC-LR 时的抗氧化反应机制和次生代谢物的生物合成，暴露期为 7、14、21 天。我们的研究表明，随着 MC-LR 暴露浓度的增加，幼苗生长受到抑制，在 1μg/L 时显著诱导，在 5μg/L 时达到最大值，而幼苗细胞中的抗氧化酶过氧化氢酶（CAT）、超氧化物歧化酶（SOD）和过氧化物酶（POD）的活性则随着 MC-LR 浓度的增加和暴露时间的延长而逐渐增加。在 5μg/L 的 MC-LR 浓度下，暴露 7 天后，丙二醛（MDA）的含量比对照组高 4.3 倍。幼苗解毒机制的研究表明，总谷胱甘肽（tGSH）和还原型谷胱甘肽（GSH）的含量，以及谷胱甘肽稀疏转移酶（GST）和谷胱甘肽还原酶（GR）的活性均有不同程度的增加，并在 1μg/L 时达到最大值。因此，MC-LR 的暴露可以促进次生代谢物的积累，并增加幼苗中次生代谢酶的活性。对这些抗氧化机制的进一步研究将为识别和开发生物标志物提供更多信息，以评估 MCs 对水生生态系统的环境影响。
