Integrative approach gives new insights into combined Cd/Cu exposure in tobacco

Abstract

Heavy metals are generally known to induce oxidative stress, but are rarely strategically studied in an embracive manner, taking into account interplay between their various effects. Furthermore, although metals in the environment are present in mixtures and interact with each other, their combined effects to organisms have been much less studied in comparison to individual effects. Here, we present a complete comprehensive study of cadmium (Cd)/copper (Cu) oxidative stress interactions in Nicotiana tabacum seedlings and adult plants. Plants were treated with Cd (10 and 15 μM), Cu (2.5 and 5 μM) and their combinations; seedlings during 1 month period and adult plants during the period of 7 days. Metal accumulation measurements showed that Cd and Cu influence each other uptake, with Cu reducing Cd translocation to shoots. PCA analysis showed that MDA and carbonyls, biomarkers of oxidative stress, as well as ascorbate peroxidase activity, highly correlated across tissues and with Cd content. Majority of toxic effects were caused by Cd-alone, while addition of Cu often resulted in damage alleviation. However, mixture of high concentrations of both Cd and Cu induced most adverse effects. In conclusion, our results indicate that Cu in lower concentration has antagonistic effect to Cd toxicity, while in higher concentration these metals interact additively in tobacco.