University of Thessaly, Department of Biochemistry and Biotechnology, Laboratory of Plant and Environmental Biotechnology, Viopolis, 41500, Larissa, Greece.
University of Thessaly, Department of Agriculture, Crop Production and Agricultural Environment, Fytokou, 38446, Nea Ionia, Volos, Greece.
Environ Pollut. 2020 Nov;266(Pt 1):115208. doi: 10.1016/j.envpol.2020.115208. Epub 2020 Jul 13.
Microcystins (MCs) are toxins produced during cyanobacterial blooms. They reach soil and translocated to plants through irrigation of agricultural land with water from MC-impacted freshwater systems. To date we have good understanding of MC effects on plants, but not for their effects on plant-associated microbiota. We tested the hypothesis that MC-LR, either alone or with other stressors present in the water of the Karla reservoir (a low ecological quality and MC-impacted freshwater system), would affect radish plants and their rhizospheric and phyllospheric microbiome. In this context a pot experiment was employed where radish plants were irrigated with tap water without MC-LR (control) or with 2 or 12 μg L of pure MC-LR (MC2 and MC12), or water from the Karla reservoir amended (12 μg L) or not with MC-LR. We measured MC levels in plants and rhizospheric soil and we determined effects on (i) plant growth and physiology (ii) the nitrifying microorganisms via q-PCR, (ii) the diversity of bacterial and fungal rhizospheric and epiphytic communities via amplicon sequencing. MC-LR and/or Karla water treatments resulted in the accumulation of MC in taproot at levels (480-700 ng g) entailing possible health risks. MC did not affect plant growth or physiology and it did not impose a consistent inhibitory effect on soil nitrifiers. Karla water rather than MC-LR was the stronger determinant of the rhizospheric and epiphytic microbial communities, suggesting the presence of biotic or abiotic stressors, other than MC-LR, in the water of the Karla reservoir which affect microorganisms with a potential role (i.e. pathogens inhibition, methylotrophy) in the homeostasis of the plant-soil system. Overall, our findings suggest that MC-LR, when applied at environmentally relevant concentrations, is not expected to adversely affect the radish-microbiota system but might still pose risk for consumers' health.
微囊藻毒素（MCs）是在蓝藻水华期间产生的毒素。它们通过灌溉受 MC 影响的淡水系统中的农田，到达土壤并转移到植物中。迄今为止，我们对 MC 对植物的影响有了很好的了解，但对其对植物相关微生物组的影响却知之甚少。我们检验了这样一个假设，即单独的 MC-LR 或与卡拉水库（低生态质量和受 MC 影响的淡水系统）水中存在的其他胁迫因子一起，会影响萝卜植物及其根际和叶际微生物组。在这种情况下，我们进行了一项盆栽实验，其中萝卜植物用不含 MC-LR 的自来水（对照）或含有 2 或 12μg/L 纯 MC-LR（MC2 和 MC12）的水，或经卡拉水库（12μg/L）或未经 MC-LR 处理的水进行灌溉。我们测量了植物和根际土壤中的 MC 含量，并确定了其对（i）植物生长和生理（ii）通过 q-PCR 测定的硝化微生物，（ii）通过扩增子测序测定的细菌和真菌根际和叶际群落多样性的影响。MC-LR 和/或卡拉水的处理导致萝卜主根中 MC 的积累水平（480-700ng/g）达到可能的健康风险水平。MC 没有影响植物的生长或生理，也没有对土壤硝化菌施加一致的抑制作用。卡拉水而不是 MC-LR 是根际和叶际微生物群落的更强决定因素，这表明卡拉水库水中存在生物或非生物胁迫因子，而不仅仅是 MC-LR，这些因子会影响在植物-土壤系统的动态平衡中具有潜在作用（即抑制病原体、甲基营养型）的微生物。总的来说，我们的研究结果表明，在环境相关浓度下，MC-LR 预计不会对萝卜-微生物组系统产生不利影响，但仍可能对消费者的健康构成威胁。
