Ectopic expression γ-glutamylcysteine synthetase of Vicia sativa increased cadmium tolerance in Arabidopsis

Glutathione (GSH) is a multifunctional essential biothiol, and its metabolism is important for plant against toxic metals and metalloids. γ-Glutamylcysteine (γ-EC), which is catalyzed by γ-Glutamylcysteine synthetase (γ-ECS), is a rate-limiting intermediate in GSH synthesis. Here, a γ-ECS gene (Vsγ-ECS) from Vicia sativa was cloned, and its function in modulating Cd tolerance was studied. Vsγ-ECS is a chloroplast localization protein, and the expression of Vsγ-ECS was upregulated by Cd stress in root of V. sativa. Heterologous expression of Vsγ-ECS (35S::Vsγ-ECS) in Arabidopsis enhanced the Cd tolerance of plants through improved primary root length, fresh weight, chlorophyll content and low degree of oxidation associated with reduced H2O2 and lipid peroxidation. However, the Cd accumulation of Arabidopsis had no effect on Vsγ-ECS overexpression. Further analysis showed that the increased Cd tolerance in 35S::Vsγ-ECS was mainly due to the capacity of increasing GSH synthesis that improved Cd chelation by GSH and phytochelatins (PCs) and alleviated the oxidative stress caused by Cd stress. In summary, a γ-ECS was characterized from V. sativa, and it demonstrated a property for increasing GSH and PC synthesis to protect plants from Cd poisoning.