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水体的富营养化加剧了蓝藻水华的频繁爆发。这不但影响水体景观效果,还会释放藻毒素,严重威胁水生态系统的稳定和公共卫生安全[1]。在众多藻毒素中,微囊藻毒素(microcystins, MCs)是一种具有显著肝脏毒性的七肽环状毒素,是世界各地水体中最为常见且危害最大的藻毒素。微囊藻毒素-LR(MC-LR)是MCs单体中分布最广毒性最强的一类,世界卫生组织(WHO)规定其在饮用水中最高含量不得超过1.0 µg·L−1[2]。鱼腥藻毒素(anatoxin, ANTXs)是一类毒性大、活性高的神经毒素,不慎接触会导致人和动物迅速中毒死亡。鱼腥藻毒素-a(ANTX-a)是鱼腥藻毒素中含量最高的一种单体,饮用水中最大安全剂量为3.0 µg·L−1[3]。在蓝藻水华频发水域,70%以上监测水体中都同时检测到MCs与ANTXs,表明两种毒素时空共存已普遍存在,且MCs或ANTXs浓度通常在1—100 µg·L−1,极端状况下会在短时间内高达1000 µg·L−1以上[4]。这些藻毒素通过灌溉、溢流、打捞堆放、堆沤还田(特别是蓝藻堆肥后施入农田)等途径进入农田系统[5-6]。研究发现,MCs被农作物吸收积累后,不仅影响农作物生长发育,如降低光合效率、破坏激素平衡、抑制抗氧化酶活性等[7-8],也会在植物可食部分积累并通过食物链传递威胁人体健康[9-10]。在调查35种农作物暴露于MCs的结果显示,MCs残留量最高的是生菜(Lactuca sativa)、欧芹(Petroselinum crispum)、茴香(Foeniculum vulgare)和卷心菜(Brassica oleracea)等蔬菜,其次是玉米(Zea mays)、胡萝卜(Daucus carota)和小麦(Hordeum vulgare)等作物[11]。因而关于藻毒素的植物毒理学研究近年来也备受关注。然而已有研究大多集中在MCs对植物生理生化代谢的影响,关于ANTXs的研究多集中在水生植物[12],关于MCs和ANTXs对植物的复合影响却鲜有报道。农作物在人类膳食结构中占有重要地位,如能明确MCs和ANTXs对农作物的复合作用机制,将为客观评价藻毒素的生态风险提供新依据,也为保障食品安全提供新的数据。
活性氧(reactive oxygen species, ROS)是植物有氧代谢中具有很强毒性的副产物,主要包括过氧化氢(H2O2)、超氧阴离子(O2·-)、羟基自由基(·OH)等[13]。作为信号分子,逆境迫使植物细胞中积累大量ROS以诱导防御基因的表达,进而调控植物对逆境的适应性。同时大量积累的ROS会引发氧化损伤,甚至导致细胞死亡[14]。因此,逆境下植物维持胞内ROS稳态是提高植物耐受性的重要机制之一。例如,MCs胁迫下水稻(Oryza sativa)中抗氧化酶清除ROS的能力强于黄瓜(Cucumis sativus),这也是水稻耐受MCs胁迫能力强于黄瓜的主要因素[8]。基于ROS水平与植物耐受环境胁迫机制的密切关系,从活性氧稳态(即产生与清除间的平衡)的角度去理解MCs和ANTXs对植物生长影响的复合作用特征,可为清晰植物耐受蓝藻毒素胁迫的适应机制提供新数据。鉴于此,本文选取广泛种植的生菜(Lactuca sativa)为研究对象,以调控活性氧生成与去除的重要酶类为切入点,探究MCs与ANTXs对生菜中活性氧稳态影响的内在机制,为客观评价蓝藻毒素的生态风险提供新的数据。
微囊藻毒素与鱼腥藻毒素对生菜活性氧稳态的复合影响
Compound effects of microcystin and anatoxin on homeostasis of reactive oxygen species in lettuce
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摘要: 水体富营养化导致水体中蓝藻毒素浓度高于安全值。为客观评价灌溉水中蓝藻毒素的生态风险,本研究探析了微囊藻毒素(MCs)和鱼腥藻毒素(ANTXs)对生菜生长和活性氧(ROS)稳态的复合影响。采用5 µg·L−1或100 µg·L−1MCs、ANTXs和MCs+ANTXs((5+5) µg·L−1或(100+100) µg·L−1)处理生菜7 d后发现,低浓度(5 µg·L−1)MCs、ANTXs或MCs+ANTXs促进生菜鲜重增加63.3%—85.6%,可能是低浓度毒素诱导SOD活性和总抗氧化能力(FRAP)上升以维持H2O2和O2·−平衡进而避免氧化损伤。高浓度(100 µg·L−1)MCs、ANTXs或MCs+ANTXs抑制生菜生长,降幅为MCs(27.7%)>MCs+ANTXs(16.8%)>ANTXs(5.1%)。同时,MDA、H2O2和O2·−含量、NADPH氧化酶活性及LsRbohA表达量、SOD和CAT活性均升高,增幅为MCs>MCs+ANTXs>ANTXs,而FRAP变化不一致。推测高浓度藻毒素上调LsRbohA表达有助于增强NADPH氧化酶活性,生成的ROS增多以刺激防御应激,而SOD和CAT活性上升不足以维持ROS稳定,导致氧化损伤而抑制生长。进一步分析MCs+ANTXs对生菜中ROS稳态复合影响的作用特征发现,MCs+ANTXs(5+5) µg·L−1对MDA、H2O2、NADP氧化酶与CAT活性影响呈现协同效应,在MCs+ANTXs(100+100) µg·L−1处理下呈拮抗效应,表明MCs和ANTXs对生菜ROS稳态的复合影响受毒素浓度的调控,一定浓度的ANTXs共存减轻了MCs对生菜的氧化伤害,为指导灌溉安全提供新的理论依据。Abstract: The eutrophication of water leads to the increase of cyanobacteria toxin concentration in water. To objectively evaluate the ecological risk of cyanobacteria toxins in irrigation water, we studied compound effects of microcystin (MCs) and anatoxin (ANTXs) on growth and homeostasis of reactive oxygen species (ROS) in lettuce. After Hydroponic lettuce being treated with MCs (5 µg·L−1 or 100 µg·L−1), ANTXs (5 µg·L−1 or 100 µg·L−1) and MCs+ANTXs (5+5) µg·L−1 or (100+100) µg·L−1 for 7 d, we found that low concentration (5 µg·L−1) of MCs, ANTXs or MCs+ANTXs increased fresh weight of lettuce by 63.3%—85.6%, indicating that the increase of SOD activity and total antioxidant capacity (FRAP) induced by low concentration of toxin can maintain H2O2 and O2·− balance and then avoid oxidative damage. However, high concentration (100 µg·L−1) of MCs, ANTXs or MCs+ANTXs inhibited lettuce growth, and the decreased degree of each treatment was MCs(27.7%)>MCs+ANTXs(16.8%)>ANTXs(5.1%). Meanwhile, MDA, H2O2 and O2·− contents, NADPH oxidase activity and LsRbohA expression, SOD and CAT activities were increased with the order for increased degree as MCs>MCs+ANTXs>ANTXs. In addition, FRAP showed different change among treatments. These results indicate that high concentration treatments up-regulated LsRbohA expression for contributing to enhancing NADPH oxidase activity to produce more ROS for stimulating defense systems. While the increase in SOD and CAT activities was not enough to maintain the stability of ROS, resulting in oxidative damage and inhibition on growth. Furthermore, characteristic analysis of compound effects of MCs+ANTXs on ROS homeostasis in lettuce showed that MCs+ANTXs (5+5) µg·L−1 posed synergistic effects on MDA and H2O2 contents as well as NADPH oxidase and CAT activities in lettuce whereas MCs+ANTXs (100+100) µg·L−1 showed antagonistic effects on them. It can be included that compound effects of MCs and ANTXs on homeostasis of ROS in lettuce was dependent on their concentrations, and the coexistence of ANTXs at a certain concentration could reduce the oxidative damage caused by MCs to lettuce, providing a new theoretical basis for guiding the safety of irrigation water.
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Key words:
- microcystins /
- anatoxin /
- NADPH oxidase /
- antioxidant enzymes /
- reactive oxygen species /
- lettuce
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表 1 MCs和ANTXs对生菜生物量、MDA、H2O2和O2·-含量的复合影响
Table 1. Combined effects of MCs and ANTXs on biomass and contents of MDA, H2O2 and O2·- in lettuce leaves
处理组
Treatments浓度/(µg·L−1)
ConcentrationFW/g MDA/(µmol·g−1 FW) H2O2/(µg·g−1 FW) O2·−/(µg·g−1 FW) CK 0 20.772±1.292c 0.74±0.06d 6.27±0.74e 4.18±0.07c MCs 5 36.415±1.290a 0.75±0.06d 5.50±0.44e 4.25±0.14c 100 15.093±0.791d 1.57±0.13a 15.83±0.66a 10.71±0.98a ANTXs 5 38.552±0.888a 0.73±0.12d 5.47±0.29e 4.86±0.11c 100 19.720±1.764c 1.24±0.10b 10.06±0.61c 8.57±0.53b MCs+ANTX 5+5 33.913±1.158b 0.89±0.03c 8.83±1.00d 4.78±0.26c 100+100 17.283±0.983d 1.37±0.08b 11.31±0.47b 8.97±0.49b 注:不同字母表示各处理组间差异显著(P<0.05). Note: Different letters represent significant differences between treatments (P<0.05). 表 2 MCs和ANTXs对生菜ROS稳态影响的复合作用特征分析
Table 2. Characteristic analysis on combined effects of MCs and ANTXs on homeostasis of ROS in lettuce
指标
IndexMCs/
(µg·L−1)A/% ANTXs/
(µg·L−1)B/% MCs+ANTXs/
(µg·L−1)C/% Cexp/% RI FW 5 −75.31 5 −85.60 5+5 −63.27 −225.36 0.28* 100 27.34 100 5.06 100+100 16.80 31.02 0.54* MDA 5 −2.22 5 1.31 5+5 −28.44 −0.88 32.44* 100 −113.39 100 −68.59 100+100 −85.52 −259.74 0.33* H2O2 5 12.24 5 12.77 5+5 −40.95 23.45 −1.75* 100 −152.58 100 −60.54 100+100 −80.44 −305.49 0.26* O2·− 5 −1.63 5 −16.11 5+5 −14.13 −18.01 0.79* 100 −155.90 100 −104.75 100+100 −114.31 −423.96 0.27* NADPH 5 5.25 5 1.38 5+5 −8.09 6.56 −1.23* 100 −81.90 100 −45.44 100+100 −62.80 −164.55 0.38* SOD 5 −20.59 5 −4.22 5+5 −16.42 −25.67 0.64* 100 −94.40 100 −32.65 100+100 −76.28 −157.86 0.48* CAT 5 2.18 5 1.72 5+5 −4.43 3.87 −1.15* 100 −66.98 100 −18.99 100+100 −49.37 −98.69 0.50* FRAP 5 −70.13 5 −86.76 5+5 −87.78 −217.73 0.40* 100 26.41 100 −17.14 100+100 11.89 13.80 0.86* 注:数据为平均值±标准误差,*代表与1之间的显著性(P<0.05).
Note: The data is denoted as mean±standard deviation, * represents the significance between RI and 1 (P<0.05). -
[1] ZHANG Y F, LIANG J, ZENG G M, et al. How climate change and eutrophication interact with microplastic pollution and sediment resuspension in shallow lakes: A review [J]. The Science of the Total Environment, 2020, 705: 135979. doi: 10.1016/j.scitotenv.2019.135979 [2] INGRID C, MARTIN W. Toxic cyanobacteria in water: A guide to their public health consequences, monitoring and management [M]. CRC Press, 2021. [3] RELLÁN S, OSSWALD J, SAKER M, et al. First detection of anatoxin-a in human and animal dietary supplements containing cyanobacteria [J]. Food and Chemical Toxicology, 2009, 47(9): 2189-2195. doi: 10.1016/j.fct.2009.06.004 [4] SVIRČEV Z, LALIĆ D, BOJADŽIJA SAVIĆ G, et al. Global geographical and historical overview of cyanotoxin distribution and cyanobacterial poisonings [J]. Archives of Toxicology, 2019, 93(9): 2429-2481. doi: 10.1007/s00204-019-02524-4 [5] CHEN W, JIA Y L, LI E H, et al. Soil-based treatments of mechanically collected cyanobacterial blooms from Lake Taihu: Efficiencies and potential risks [J]. Environmental Science & Technology, 2012, 46(24): 13370-13376. [6] AI Y H, LEE S, LEE J. Drinking water treatment residuals from cyanobacteria bloom-affected areas: Investigation of potential impact on agricultural land application [J]. The Science of the Total Environment, 2020, 706: 135756. doi: 10.1016/j.scitotenv.2019.135756 [7] LIANG C J, WANG W M, WANG Y. Effect of irrigation with microcystins-contaminated water on growth, yield and grain quality of rice (Oryza sativa) [J]. Environmental Earth Sciences, 2016, 75(6): 1-10. [8] GU Y F, LIANG C J. Responses of antioxidative enzymes and gene expression in Oryza sativa L and Cucumis sativus L seedlings to microcystins stress [J]. Ecotoxicology and Environmental Safety, 2020, 193: 110351. doi: 10.1016/j.ecoenv.2020.110351 [9] ZHU J Z, REN X Q, LIU H Y, et al. Effect of irrigation with microcystins-contaminated water on growth and fruit quality of Cucumis sativus L. and the health risk [J]. Agricultural Water Management, 2018, 204: 91-99. doi: 10.1016/j.agwat.2018.04.011 [10] LIANG C J, MA X D, LIU H Y. Effect of microcystins at different rice growth stages on its yield, quality, and safety [J]. Environmental Science and Pollution Research, 2021, 28(11): 13942-13954. doi: 10.1007/s11356-020-11642-x [11] ZHANG Y Y, WHALEN J K, SAUVÉ S. Phytotoxicity and bioconcentration of microcystins in agricultural plants: Meta-analysis and risk assessment [J]. Environmental Pollution, 2021, 272: 115966. doi: 10.1016/j.envpol.2020.115966 [12] KAMINSKI A, BOBER B, CHRAPUSTA E, et al. Phytoremediation of anatoxin-a by aquatic macrophyte Lemna trisulca L [J]. Chemosphere, 2014, 112: 305-310. doi: 10.1016/j.chemosphere.2014.04.064 [13] LIN Y F, LIN H T, ZHANG S, et al. The role of active oxygen metabolism in hydrogen peroxide-induced pericarp browning of harvested longan fruit [J]. Postharvest Biology and Technology, 2014, 96: 42-48. doi: 10.1016/j.postharvbio.2014.05.001 [14] 孙亮亮. 镧对拟南芥种子萌发和早期根系发育影响的生理与分子机制研究[D]. 太谷: 山西农业大学, 2018. SUN L L. Physiological and molecular mechanisms of La on seed germination and early root development of Arabidopsis thaliana[D]. Taigu: Shanxi Agricultural University, 2018(in Chinese).
[15] MARTENS S. Handbook of cyanobacterial monitoring and cyanotoxin analysis [J]. Advances in Oceanography and Limnology, 2017, 8(2): 242. [16] 张清航, 张永涛. 植物体内丙二醛(MDA)含量对干旱的响应 [J]. 林业勘查设计, 2019(1): 110-112. doi: 10.3969/j.issn.1673-4505.2019.01.052 ZHANG Q H, ZHANG Y T. Study on response to drought stress of MDA content in plants [J]. Forest Investigation Design, 2019(1): 110-112(in Chinese). doi: 10.3969/j.issn.1673-4505.2019.01.052
[17] 曹翠玲, 麻鹏达. 植物生理学教学实验指导[M]. 杨凌: 西北农林科技大学出版社, 2016. CAO C L, MA P D. Experimental Study on plant Physiology teaching [M]. Yangling: Northwest A&F University Press, 2016(in Chinese).
[18] KUMAR A, PRASAD M N V, MOHAN MURALI ACHARY V, et al. Elucidation of lead-induced oxidative stress in Talinum triangulare roots by analysis of antioxidant responses and DNA damage at cellular level [J]. Environmental Science and Pollution Research, 2013, 20(7): 4551-4561. doi: 10.1007/s11356-012-1354-6 [19] 关美艳. 一氧化氮清除系统在拟南芥应答镉胁迫过程中的作用及其机制[D]. 杭州: 浙江大学, 2018. GUAN M Y. The mechanisms of nitric oxide scavenging systems in regulating Arabidopsis response to cadmium stress[D]. Hangzhou: Zhejiang University, 2018(in Chinese).
[20] ZHANG B J, BU J J, LIANG C J. Regulation of nitrogen and phosphorus absorption by plasma membrane H+ ATPase in rice roots under simulated acid rain [J]. International Journal of Environmental Science and Technology, 2017, 14(1): 101-112. doi: 10.1007/s13762-016-1125-x [21] STOJNIĆ S, KOVAČEVIĆ B, KEBERT M, et al. Genetic differentiation in functional traits among wild cherry (Prunus avium L. ) half-sib lines [J]. Journal of Forestry Research, 2022, 33(3): 991-1003. doi: 10.1007/s11676-021-01390-0 [22] 顾艳芳, 邓媛, 梁婵娟. 微囊藻毒素对黄瓜幼苗抗氧化酶及其同工酶的影响 [J]. 环境化学, 2020, 39(12): 3402-3409. GU Y F, DENG Y, LIANG C J. Effect of microcystins on antioxidative enzymes activities and isozymes pattern in cucumber seedlings [J]. Environmental Chemistry, 2020, 39(12): 3402-3409(in Chinese).
[23] CAO Q, STEINMAN A D, WAN X, et al. Combined toxicity of microcystin-LR and copper on lettuce (Lactuca sativa L. ) [J]. Chemosphere, 2018, 206: 474-482. doi: 10.1016/j.chemosphere.2018.05.051 [24] RASTOGI R P, SINHA R P, INCHAROENSAKDI A. The cyanotoxin-microcystins: Current overview [J]. Reviews in Environmental Science and Bio/Technology, 2014, 13(2): 215-249. doi: 10.1007/s11157-014-9334-6 [25] LIANG C J, LIU H Y. Response of hormone in rice seedlings to irrigation contaminated with cyanobacterial extract containing microcystins [J]. Chemosphere, 2020, 256: 127157. doi: 10.1016/j.chemosphere.2020.127157 [26] CHRISTENSEN V G, KHAN E. Freshwater neurotoxins and concerns for human, animal, and ecosystem health: A review of anatoxin-a and saxitoxin [J]. The Science of the Total Environment, 2020, 736: 139515. doi: 10.1016/j.scitotenv.2020.139515 [27] 杨颖丽, 安黎哲, 张立新. NaCl对小麦根质膜NADPH氧化酶活性的影响 [J]. 西北植物学报, 2006, 26(12): 2463-2467. doi: 10.3321/j.issn:1000-4025.2006.12.010 YANG Y L, AN L Z, ZHANG L X. NaCl effect on plasmalemma NADPH oxidase activity of wheat roots [J]. Acta Botanica Boreali-Occidentalia Sinica, 2006, 26(12): 2463-2467(in Chinese). doi: 10.3321/j.issn:1000-4025.2006.12.010
[28] 张腾国, 赖晶, 李萍, 等. 不同处理下油菜RbohA、RbohD基因的表达特性分析 [J]. 生态学杂志, 2019, 38(1): 173-180. doi: 10.13292/j.1000-4890.201901.024 ZHANG T G, LAI J, LI P, et al. Expression analysis of RbohA and RbohD genes in Brassica campestris under different treatments [J]. Chinese Journal of Ecology, 2019, 38(1): 173-180(in Chinese). doi: 10.13292/j.1000-4890.201901.024
[29] ZHANG J Z, WANG L H, ZHOU Q, et al. Reactive oxygen species initiate a protective response in plant roots to stress induced by environmental bisphenol A [J]. Ecotoxicology and Environmental Safety, 2018, 154: 197-205. doi: 10.1016/j.ecoenv.2018.02.020 [30] PÉREZ-CHACA M V, RODRÍGUEZ-SERRANO M, MOLINA A S, et al. Cadmium induces two waves of reactive oxygen species in Glycine max (L. ) roots [J]. Plant, Cell & Environment, 2014, 37(7): 1672-1687. [31] SHABIR H, VINAY K, VARSHA S, et al. Phytohormones and their metabolic engineering for abiotic stress tolerance in crop plants [J]. Crop Journal, 2016, 4(3): 162-176. doi: 10.1016/j.cj.2016.01.010 [32] 朱婷婷, 王彦霞, 裴丽丽, 等. 植物蛋白激酶与作物非生物胁迫抗性的研究 [J]. 植物遗传资源学报, 2017, 18(4): 763-770. doi: 10.13430/j.cnki.jpgr.2017.04.020 ZHU T T, WANG Y X, PEI L L, et al. Research progress of plant protein kinase and abiotic stress resistance [J]. Journal of Plant Genetic Resources, 2017, 18(4): 763-770(in Chinese). doi: 10.13430/j.cnki.jpgr.2017.04.020
[33] LIANG C J, ZHANG Y Q, REN X Q. Calcium regulates antioxidative isozyme activity for enhancing rice adaption to acid rain stress [J]. Plant Science, 2021, 306: 110876. doi: 10.1016/j.plantsci.2021.110876 [34] MA Y J, REN X Q, LIANG C J. Exogenous Ca2+ enhances antioxidant defense in rice to simulated acid rain by regulating ascorbate peroxidase and glutathione reductase [J]. Planta, 2021, 254(2): 41-44. doi: 10.1007/s00425-021-03679-0 [35] CHRISTINE H F, GRAHAM N. Redox sensing and signalling associated with reactive oxygen in chloroplasts, peroxisomes and mitochondria [J]. Physiologia Plantarum, 2003, 119(3): 355-364. doi: 10.1034/j.1399-3054.2003.00223.x [36] WANG Z, ZHANG J Q, LI E H, et al. Combined toxic effects and mechanisms of microsystin-LR and copper on Vallisneria Natans (Lour. ) Hara seedlings [J]. Journal of Hazardous Materials, 2017, 328: 108-116. doi: 10.1016/j.jhazmat.2016.12.059 [37] LI Q, GU P, ZHANG C, et al. Combined toxic effects of anatoxin-a and microcystin-LR on submerged macrophytes and biofilms [J]. Journal of Hazardous Materials, 2020, 389: 122053. doi: 10.1016/j.jhazmat.2020.122053 [38] 张雪薇. 铜绿微囊藻与水华鱼腥藻种间竞争机制的初步研究[D]. 南京: 南京大学, 2012. ZHANG X W. The preliminary study of the mechanism of competition between Microcystis aeruginosa and Anabaena flos-aquae[D]. Nanjing: Nanjing University, 2012(in Chinese).