Cadmium induced glutathione bioaccumulation mediated by γ-glutamylcysteine synthetase in ectomycorrhizal fungus Hebeloma cylindrosporum
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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.
KeywordsEctomycorrhizal fungi Metal homeostasis γ-Glutamylcysteine synthetase Hebeloma cylindrosporum Glutathione Cadmium
Authors are thankful to Department of Biotechnology, Govt. of India for sponsoring the research Project (BT/PR8339/BCE/8/1045/2013) to carry out the present work.
The authors report no financial interest or benefit arising from the direct application of this work.
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The authors report no conflict of interest.
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