Heavy metals produced macromolecules oxidation and modified proteolytic activity in sunflower leaves

LB PENA; LA PASQUINI; ML TOMARO; SM GALLEGO

Rosario, Santa Fe

Congreso; XLII Reunión anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2006

SAIB

The increase and availability of metal in soil has initiated extensive studies about their tolerance-toxicity in plants. A comparative analysis about the effect of 100 µM of AlCl3, CoCl2, CuCl2, CrCl3, HgCl2, NiCl2, PbCl2 or ZnCl2 on macromolecules oxidation and modified proteolytic activity was performed in sunflower leaves after 4 days of plant treatment. Except Pb, metals caused a decrease in leaf area. Co, Cr, Cu and Hg increased lipid peroxidation. Total proteins shared similar patterns, however, Co, Cu, Hg and Ni produced proteins oxidation, specially with molecular weight lower than 150 kDa. Except Al and Zn that increased acid proteases activity, the rest of metals decreased it. Similar pattern was observed with neutral activity. While Co and Pb decreased basic activity; Cu, Hg and Zn increased it. Metals decreased 20S proteasome hydrolyzing activities. Nor protein fragmentation either modification in the proteasoma protein abundance was observed (except Hg that decreased 20S protein). New bands with low molecular weight of ubiquitin conjugated proteins were observed with Al, Cr, Cu, Hg and Ni treatment. In order to understand the different mechanisms of metal toxicity and the plant response certain common features can be established that included decline in the antioxidant defense system, increase of ROS production, or diminished capacity for removal of oxidized proteins.