Ectomycorrhizal fungi hold a potential role in bioremediation of heavy metal polluted areas because of its metal accumulation and detoxification property. We investigated the cadmium (Cd) induced bioaccumulation of glutathione (GSH) mediated by γ-glutamylcysteine synthetase (γ-GCS) in the ectomycorrhizal fungus Hebeloma cylindrosporum. In H. cylindrosporum, a demand driven synthesis of GSH has been observed in response to Cd. The expression and enzyme activity of H. cylindrosporum γ-GCS (Hcγ-GCS) increased as a function of external Cd stress resulting in increased GSH production. The function of Hcγ-GCS in providing heavy metal tolerance to H. cylindrosporum was justified by complementing the gene in gsh1Δ mutant of Saccharomyces cerevisiae. The metal sensitive mutant gsh1Δ successfully restored its metal tolerance ability when transformed with Hcγ-GCS gene. Sequence analysis of Hcγ-GCS showed homology with most of the reported γ-GCS proteins from basidiomycetes family. The active site of the Hcγ-GCS protein is composed of amino acids that were found to be conserved not only in fungi, but also in plants and mammals. From these results, it was concluded that Hcγ-GCS plays an important role in bioaccumulation of GSH, which is a core component in the mycorrhizal defense system under Cd stress for Cd homeostasis and detoxification.

中文翻译：

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γ-谷氨酰半胱氨酸合成酶介导的镉诱导的外生菌根真菌Hebeloma cylindrosporum中的谷胱甘肽生物富集。

外生菌根真菌由于其金属积累和解毒特性，在重金属污染区的生物修复中具有潜在作用。我们调查了由镉（Cd）诱导的γ-谷氨酰半胱氨酸合成酶（γ-GCS）介导的外生菌根真菌Hebeloma cylindrosporum中谷胱甘肽（GSH）的生物富集。在H.cylindrosporum中，已观察到响应镉的需求驱动的GSH合成。圆柱孢子菌γ-GCS（Hcγ-GCS）的表达和酶活性随外部Cd胁迫而增加，导致GSH产生增加。通过对酿酒酵母gsh1Δ突变体中的基因进行补充，证明了Hcγ-GCS在提供对圆柱孢菌的重金属耐受性中的功能。用Hcγ-GCS基因转化的金属敏感性突变体gsh1Δ成功恢复了其金属耐受能力。Hcγ-GCS的序列分析显示与来自担子菌家族的大多数报道的γ-GCS蛋白具有同源性。Hcγ-GCS蛋白的活性位点由氨基酸组成，这些氨基酸不仅在真菌中而且在植物和哺乳动物中都是保守的。从这些结果可以得出结论，Hcγ-GCS在GSH的生物蓄积中起着重要作用，GSH是Cd胁迫下Cd稳态和排毒的菌根防御系统的核心成分。而且在植物和哺乳动物中 从这些结果可以得出结论，Hcγ-GCS在GSH的生物蓄积中起着重要作用，GSH是Cd胁迫下Cd稳态和排毒的菌根防御系统的核心成分。而且在植物和哺乳动物中 从这些结果可以得出结论，Hcγ-GCS在GSH的生物蓄积中起着重要作用，GSH是Cd胁迫下Cd稳态和排毒的菌根防御系统的核心成分。