Quantitative changes in protein expression of cadmium-exposed poplar plants

Cadmium (Cd) pollution is a worldwide major concern having, among others, deleterious effects on plants. In the present work, the effects of a 20 microM Cd exposure in hydroponics culture during 14 days were evaluated in young poplar leaves. Proteins were analysed by 2-D DIGE, followed by MALDI-TOF-TOF identification. Additionally, growth and other physiological parameters were monitored during the experiment. Treated plants exhibited an inhibition of growth and visual symptoms appeared after 7 days. A significant accumulation of Cd in all organs was recorded by ICP-MS analysis. A number of changes in the expression of proteins with various functions were identified; in particular a decreased abundance of oxidative stress regulating proteins, whereas pathogenesis-related proteins showed a drastic increase in abundance. Furthermore, a large number of proteins involved in carbon metabolism showed a decrease in abundance, while proteins involved in remobilizing carbon from other energy sources were upregulated. In conclusion, the negative effect of Cd could be explained by a deleterious effect on protein expression from the primary carbon metabolism and from the oxidative stress response mechanism. Accumulation of Cd in stems of poplar, coupled with a low impact of Cd on physiological parameters, promotes the use of poplar trees for phytoremediation purposes.