Synergistic inhibition of the growth of suspension cultured tobacco cells by simultaneous treatment with cadmium and arsenic in relation to phytochelatin synthesis

Abstract

Abstract Simultaneous treatments with Cd and arsenic (arsenite and arsenate) led to the synergistic growth inhibition of tobacco (Nicotiana tabacum cv. BY-2) cells. Cd contents in cells increased by co-treatment with arsenic for 24 h. The amount of total phytochelatins (PCs) per unit of Cd in the cells treated with Cd and arsenate was lower than that in the cells treated with Cd alone. Simultaneous treatments with Cd and arsenic promoted the induction of the biosynthesis of (γ-Glu-Cys)2-Gly and inhibited the induction of the biosynthesis of (γ-GluCys)3-Gly and (γ-Glu-Cys)4-Gly, compared with the treatment with Cd alone. Consequently, since the inhibition of PC biosynthesis led to the increase of the cellular concentration of putative ionic (= toxic) Cd, cell growth was inhibited synergistically by simultaneous treatments with Cd and arsenic. In addition, based on the results showing that buthionine sulfoximine increased the sensitivity to arsenite and arsenate, that PC biosynthesis was induced by treatment with arsenite or arsenate, it is suggested that glutathione and/or its metabolic products such as PCs are involved in arsenic tolerance.