Cadmium-induced changes in glutathione and phenolics of Thlaspi and Noccaea species differing in Cd accumulation

Glutathione (GSH) and phenolics play an important role in plant defense against metal-ion toxicity. The antioxidant activity and metal-binding capacity of these compounds can account for the protective effects. In contrast to animal-cell models, however, the possible interplay among these substances in stress defense of plants is poorly investigated. This study compares the influence of cadmium (Cd) on the profiles of both soluble phenolics and GSH in shoots of different Thlaspi and Noccaea species: two ecotypes of the nonhyperaccumulator T. arvense differing in Cd resistance (ecotype Aigues Vives, Cd-sensitive, and ecotype Jena, Cd-resistant) and two Cd-tolerant Cd-Zn hyperaccumulators N. praecox and N. caerulescens (formerly Thlaspi praecox and T. caerulescens). To reveal the possible influence of Cd-induced sulfur (S) shortage on the stress response, plants receiving normal S concentrations (500 μM MgSO4) and plants treated with surplus S (500 μM MgSO4 + 500 μM K2SO4) were analyzed. Our working hypothesis was that species differences in tolerance to high tissue Cd concentrations should be reflected by differences in endogenous levels of GSH and phenolic compounds. The results reveal clear species-dependent differences in both the constitutive patterns and the Cd- and S-induced changes in shoot concentrations of GSH and phenolics. However, no simple relationship between these shoot concentrations and Cd accumulation and tolerance can be established. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.