The Influence of Cadmium Stress on the Content of Mineral Nutrients and Metal-Binding Proteins in Arabidopsis halleri

Abstract

We investigated the influence of cadmium stress on zinc hyperaccumulation, mineral nutrient uptake, and the content of metal-binding proteins in Arabidopsis halleri. The experiments were carried out using plants subjected to long-term cadmium exposure (40 days) in the concentrations of 45 and 225 μM Cd(2+). Inductively coupled plasma-mass spectrometry, size exclusion chromatography coupled with plasma-mass spectrometry, and laser ablation inductively coupled plasma-mass spectrometry used for ablation of polyacylamide gels were employed to assess the content of investigated elements in plants as well as to identify metal-binding proteins. We found that A. halleri is able to translocate cadmium to the aerial parts in high amounts (translocation index >1). We showed that Zn content in plants decreased significantly with the increase of cadmium content in the growth medium. Different positive and negative correlations between Cd content and mineral nutrients were evidenced by our study. We identified more than ten low-molecular-weight (<100 kDa) Cd-binding proteins in Cd-treated plants. These proteins are unlikely to be phytochelatins or metallothioneins. We hypothesize that low-molecular-weight Cd-binding proteins can be involved in cadmium resistance in A. halleri. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s11270-012-1292-4) contains supplementary material, which is available to authorized users.

Fig. 1

Total concentration of Cd (a) and Zn (b) in A. halleri extracts from shoots and roots, respectively. Metal concentration was quantified using ICP-MS

Fig. 2

a-f SEC-ICP-MS electropherogram of ¹¹²Cd⁺, ⁶⁶Zn⁺, and ⁶⁴Cu⁺ intensity in A. halleri extracts from roots [control plants (a), plants treated with 45 μM Cd (b), plants treated with 225 μM Cd (c)], and shoots [control plants (d), plants treated with 45 μM Cd (e), plants treated with 225 μM Cd (f)]. The signal from ¹¹²Cd⁺ is designated by the solid line; the signal from ⁶⁶Zn⁺ is designated by the dashed line, and the signal from ⁶⁴Cu⁺ is designated by the dotted line

Fig. 3

SDS-PAGE gel stained with Coomassie blue (right panels) and ¹¹²Cd⁺ intensity for PAGE-LA-ICP-MS (left panels) of A. halleri extracts from roots (a) and from shoots (b)