Abstract Evidence accumulated in recent years supports the crucial role of remodeled cell walls (CWs) in enabling plants to adapt to environmental challenges. However, the metal tolerance and alleviation mechanisms involving the CWs by endophyte-plant interactions to toxic metals have not yet been elucidated. In the present study, these mechanisms are tested by exploring the maize (Zea mays) Cd tolerance by modifying its root CW structure via inoculation with a dark septate endophyte (DSE) fungus Exophiala pisciphila. Our present study demonstrates that the root CWs were the primary site for Cd accumulation, functioning as a sink for toxic Cd ions. Interestingly, E. pisciphila colonization significantly bioaugmented subcellular compartmentalization of maize roots and increased the Cd content of various CW subfractions through a significantly increased enzyme activity, e.g., pectin methylesterase, as well as an upregulated expression of genes involved in CW biosynthesis and changes in the contents of functional groups in pectin and hemicellulose 1 in response to Cd stress. Consequently, the enhanced Cd compartmentation in plant CWs by DSE lowers the entry of trace metals in the protoplast, thereby conferring the tolerant races of plants that can survive and thrive on metal-contaminated soils.

中文翻译：

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深色有隔内生菌通过重塑的宿主细胞壁和改变的 Cd 亚细胞分布增强玉米镉 (Cd) 耐受性

摘要 近年来积累的证据支持重塑细胞壁 (CW) 在使植物适应环境挑战方面的关键作用。然而，内生植物-植物对有毒金属的相互作用涉及 CW 的金属耐受性和缓解机制尚未阐明。在本研究中，通过接种深色有隔内生菌 (DSE) 真菌 Exophiala pisciphila 修改其根 CW 结构，探索玉米 (Zea mays) Cd 耐受性来测试这些机制。我们目前的研究表明，根 CWs 是 Cd 积累的主要场所，充当有毒 Cd 离子的汇。有趣的是，E。pisciphila 定植显着增强了玉米根的亚细胞区室化，并通过显着增加的酶活性（例如果胶甲酯酶）以及参与 CW 生物合成的基因表达上调和功能基团含量的变化，增加了各种 CW 亚组分的 Cd 含量在果胶和半纤维素 1 中响应 Cd 胁迫。因此，DSE 在植物 CW 中增强的 Cd 区室降低了原生质体中痕量金属的进入，从而赋予植物能够在受金属污染的土壤中生存和繁衍的耐受性小种。以及参与 CW 生物合成的基因的表达上调以及果胶和半纤维素 1 中功能基团含量的变化以响应 Cd 胁迫。因此，DSE 在植物 CW 中增强的 Cd 区室降低了原生质体中痕量金属的进入，从而赋予植物能够在受金属污染的土壤中生存和繁衍的耐受性小种。以及参与 CW 生物合成的基因的表达上调以及果胶和半纤维素 1 中功能基团含量的变化以响应 Cd 胁迫。因此，DSE 在植物 CW 中增强的 Cd 区室降低了原生质体中痕量金属的进入，从而赋予植物能够在受金属污染的土壤中生存和繁衍的耐受性小种。