College of Resources and Environmental Sciences, China Agricultural University, Beijing, 100193, China; Beijing Key Laboratory of Biodiversity and Organic Farming, China Agricultural University, Beijing, 100193, China.
College of Resources and Environmental Sciences, China Agricultural University, Beijing, 100193, China; Beijing Key Laboratory of Biodiversity and Organic Farming, China Agricultural University, Beijing, 100193, China.
Ecotoxicol Environ Saf. 2020 Jun 15;196:110540. doi: 10.1016/j.ecoenv.2020.110540. Epub 2020 Apr 3.
By testing time-dependent IC of luteolin against Microcystis growth, this study revealed 6.5 mg/L as nearly IC value during prolonged stress until day 14, and explored chlorophyll-a (CLA) and phycobiliproteins (PBPs) contents, antioxidant responses and microcystin (MC)-production/-release dynamics at rising luteolin doses (0.5~2-fold IC). Growth inhibition ratio (GIR) generally rose at rising luteolin dose, while at each dose GIR firstly increased and then leveled off or dropped. In early stage, CLA, allophycocyanin (APC), phycoerythrin (PE) and glutathione (GSH) contents, and superoxide dismutase (SOD) and catalase (CAT) activities, were increasingly stimulated at rising luteolin dose to enhance energy yield and antioxidant defense, but Microcystis was damaged more severely at rising dose, due to stress-repair imbalance. Such more severe damage in early stage, coupled with stronger PBPs-inhibition in mid-late stage, at rising dose could jointly account for rising GIR at rising dose. The CAT/GSH-stimulation persisting until late stage could alleviate cell damage in late stage, which explained for why GIR no longer increased in late stage at each luteolin dose. Besides, more MCs were produced and retained in cell to exert protective roles against luteolin-stress in early stage, but intracellular MCs decreased following inhibited MC-production by prolonged stress to decrease cell protectant. Extracellular MCs detection showed that less MCs amount existed in water phase than control along luteolin-stress, implying luteolin as eco-friendly algaecide with promising potential to remove MPM blooms and MC-risks. This is the first study to reveal the effect of various luteolin doses on MC-production/release and PBP-synthesis dynamics of Microcystis during prolonged stress. The findings shed novel views in anti-algal mechanisms of luteolin, and provided direct evidence for luteolin applied as safe agent to remediate Microcystis-dominant blooms.
通过测试木犀草素对微囊藻生长的时间依赖性抑制作用，本研究发现延长胁迫至第 14 天时，近 IC 值为 6.5mg/L，并在不断增加木犀草素剂量（0.5-2 倍 IC）的情况下，研究了叶绿素-a（CLA）和藻蓝蛋白（PBPs）含量、抗氧化响应以及微囊藻毒素（MC）的产生/释放动态。随着木犀草素剂量的增加，抑制率（GIR）普遍升高，而在每个剂量下，GIR 先升高然后趋于平稳或下降。在早期，随着木犀草素剂量的增加，CLA、别藻蓝蛋白（APC）、藻红蛋白（PE）和谷胱甘肽（GSH）含量以及超氧化物歧化酶（SOD）和过氧化氢酶（CAT）活性均受到刺激，以增强能量产生和抗氧化防御能力，但由于应激修复失衡，微囊藻在较高剂量下受到的损伤更为严重。这种在早期更为严重的损伤，再加上中晚期更强的 PBPs 抑制作用，在较高剂量下共同导致了剂量依赖性的 GIR 升高。CAT/GSH 的持续刺激直到后期，可以缓解后期的细胞损伤，这解释了为什么在每个木犀草素剂量下，GIR 在后期不再增加。此外，在早期更多的 MCs 被产生并保留在细胞中，以发挥对木犀草素胁迫的保护作用，但随着长期胁迫抑制 MC 产生，细胞内的 MCs 减少，从而减少了细胞保护剂。细胞外 MCs 的检测表明，在木犀草素胁迫期间，存在于水相中的 MCs 数量比对照少，这表明木犀草素作为一种环保型杀藻剂，具有去除微囊藻水华和 MC 风险的潜在应用前景。这是首次研究不同木犀草素剂量对延长胁迫期间微囊藻 MC 产生/释放和 PBP 合成动态的影响。这些发现为木犀草素的抗藻机制提供了新的视角，并为将木犀草素作为安全药剂应用于修复微囊藻优势水华提供了直接证据。
