Department of Agronomy in the Tropics and Subtropics, Institute of Agricultural Sciences in the Tropics (Hans-Ruthenberg-Institute), University of Hohenheim, 70593, Stuttgart, Germany.
Department of Crop Physiology of Specialty Crops, Institute of Crop Science, University of Hohenheim, 70593, Stuttgart, Germany.
Mycorrhiza. 2023 Mar;33(1-2):23-32. doi: 10.1007/s00572-022-01100-6. Epub 2023 Jan 10.
Mercury (Hg) pollution of soils is a critical environmental problem. To rehabilitate Hg contaminated soils, arbuscular mycorrhizal (AM) fungi-based phytoremediation may be supportive, yet the functional potential of AM fungi in response to Hg exposure is unclear. In a greenhouse experiment, we assessed the response of Medicago truncatula (Hg tolerance index (TI), Hg partitioning) to different Hg concentrations [0 (Hg0), 25 (Hg25), 50 (Hg50) µg g] in treatments with (AM) and without (NM) inoculation of Rhizophagus irregularis. Additionally, zinc (Zn) uptake and the expression of two Zn transporter genes (ZIP2, ZIP6) were examined because Zn is an essential element for plants and shares the same outer electronic configuration as Hg, implying potential competition for the same transporters. The results showed that AM plants had a higher TI than NM plants. Plant roots were identified as dominant Hg reservoirs. AM inoculation reduced the root Hg concentration under Hg50 compared to the NM treatment. There was an interaction between Hg treatment and AM inoculation on Hg stem concentration, i.e., at Hg25, AM inoculation decreased the Hg translocation from roots to stems, while Hg translocation was increased at Hg50 compared to the NM treatment. Zn acquisition was improved by R. irregularis. The negative relationship between Hg and Zn concentrations in the roots of AM and NM plants implied potential competition for the same transporters, although the expression of Zn transporters was upregulated by AM inoculation at all Hg levels. In conclusion, this baseline study demonstrated that R. irregularis may play an important role in Hg tolerance of M. truncatula, suggesting its potential for Hg-contaminated phytoremediation.
土壤汞污染是一个严峻的环境问题。为了修复汞污染土壤，丛枝菌根（AM）真菌的植物修复可能会有所帮助，但 AM 真菌对汞暴露的功能潜力尚不清楚。在温室实验中，我们评估了紫花苜蓿（汞耐受指数（TI）、汞分配）对不同汞浓度[0（Hg0）、25（Hg25）、50（Hg50）μg g]的响应，处理方法为接种（AM）和不接种（NM）Rhizophagus irregularis。此外，还研究了锌（Zn）的吸收和两个 Zn 转运基因（ZIP2、ZIP6）的表达，因为 Zn 是植物的必需元素，并且与 Hg 具有相同的外层电子构型，这意味着它们可能对相同的转运体存在竞争。结果表明，AM 植物的 TI 高于 NM 植物。植物根系是汞的主要蓄积库。与 NM 处理相比，AM 接种在 Hg50 下降低了根中的汞浓度。Hg 处理与 AM 接种之间对茎中 Hg 浓度存在相互作用，即在 Hg25 时，AM 接种减少了从根部到茎部的 Hg 转运，而与 NM 处理相比，Hg50 时的 Hg 转运增加。R. irregularis 提高了 Zn 的获取。AM 和 NM 植物根系中 Hg 和 Zn 浓度之间的负相关关系表明它们可能对相同的转运体存在竞争，尽管在所有 Hg 水平下，AM 接种都上调了 Zn 转运体的表达。总之，这项基础研究表明，R. irregularis 可能在 M. truncatula 的汞耐受中发挥重要作用，这表明其在汞污染植物修复中的潜力。
