Metals and plants: between nutrition and toxicity

MP BENAVIDES; LB PENA; CE AZPILICUETA; SM GALLEGO

Mendoza. Argentina

Simposio; XXVIII Reunión cintífica de la Sociedad de Biología de Cuyo; 2010

Sociedad de Biología de Cuyo

Metals represent an essential fraction of the elements required by plants to carry out their life cycle. However, an excess some of these metals in the soil or the presence of others considered as non-essential ones can be toxic for the plants. Metal toxicity is associated with the generation oxidative stress, evidenced by an increase in lipid and protein oxidation and modification of the antioxidant defence system. Although phytochelatin production is a mechanism involved in plant cell metal detoxification, their syntheses can decrease glutathione content, one of the main soluble antioxidants. Metals mediated protein oxidation can alter protein functionality. In this sense, inactivation of catalase (CAT) enzyme by protein oxidation was observed in sunflower plants treated with Cd and Cu. Interestingly, in this plant species, genes coding for CAT isoforms less sensible to oxidation were up-regulated. On the other hand, both Cd and Cu proved to alter proteasome system through oxidative modification of the 20S proteasome complex, which prevents accumulation of oxidative damaged proteins in the cell. Under severe Cd stress, sunflower proteasome activity is reduced and this results in accumulation of oxidized proteins. Although plant cell proteolysis is modified by the presence of metals, no correlation could be observed between proteolysis extent and metal toxicity. Data relating the oxidative status of the cell to plant growth will be presented and discussed