Search

• Ws plants are less sensitive to excess Cu than Col-0 plants • Ws roots cope better with an altered Cu homeostasis as compared to Col-0 roots • Cd exposure induces a Cu deficiency response in Ws and Col-0 roots • Ws roots counteract Cd-induced Cu deficiency more efficiently than Col-0 roots The commonly used Arabidopsis thaliana natural accessions Columbia (Col-0) and Wassilewskija (Ws) are known to differ in their metal sensitivity, with Col-0 being more sensitive to copper (Cu) and cadmium (Cd) than Ws. As both Cu and Cd are known to affect Cu homeostasis, it was investigated whether this process is part of an accession-specific mechanism underlying their difference in metal sensitivity. As roots are the first contact point during metal exposure, responses were compared between roots of both accessions of hydroponically grown plants exposed to excess Cu or Cd for 24 and 72 h. Root Cu levels increased in both accessions under Cu and Cd exposure. However, under Cu exposure, the downregulation of Cu transporter (COPT) genes in combination with a more pronounced upregulation of metallothionein gene MT2b indicated that Ws plants coped better with the elevated Cu concentrations. The Cd-induced disturbance in Cu homeostasis was more efficiently counteracted in roots of Ws plants than in Col-0 plants. This was indicated by a higher upregulation of the SPL7-mediated pathway, crucial in the regulation of the Cu homeostasis response. In conclusion, maintaining the Cu homeostasis response in roots is key to accession-specific differences in Cu and Cd sensitivity. [ABSTRACT FROM AUTHOR]

The cellular redox state is an important determinant of metal phytotoxicity. In this study we investigated the influence of cadmium (Cd) and copper (Cu) stress on the cellular redox balance in relation to oxidative signalling and damage in Arabidopsis thaliana. Both metals were easily taken up by the roots, but the translocation to the aboveground parts was restricted to Cd stress. In the roots, Cu directly induced an oxidative burst, whereas enzymatic ROS (reactive oxygen species) production via NADPH oxidases seems important in oxidative stress caused by Cd. Furthermore, in the roots, the glutathione metabolism plays a crucial role in controlling the gene regulation of the antioxidative defence mechanism under Cd stress. Metal-specific alterations were also noticed with regard to the microRNA regulation of CuZnSOD gene expression in both roots and leaves. The appearance of lipid peroxidation is dual: it can be an indication of oxidative damage as well as an indication of oxidative signalling as lipoxygenases are induced after metal exposure and are initial enzymes in oxylipin biosynthesis. In conclusion, the metal-induced cellular redox imbalance is strongly dependent on the chemical properties of the metal and the plant organ considered. The stress intensity determines its involvement in downstream responses in relation to oxidative damage or signalling., (Copyright © 2010 Elsevier GmbH. All rights reserved.)