Effect of cadmium stress on protein synthesis and degradation in sunflower (Helianthus annuus L.) leaves

PENA LB; LA PASQUINI; ML TOMARO; SM GALLEGO

Iguazú, Misiones

Congreso; XL Reunión Anual Sociedad Argentina de Investigación Bioquímica y Biología Molecular; 2004

SAIB

The effect of oxidative stress induced by cadmium on growth parameters and the balance between protein synthesis and degradation in sunflower (Helianthus annuus L.) leaves were studied. Plants were germinated 10 d and then transferred to hydroponics medium devoid (control) or containing 100, 200 and 300 µM CdCl2. Analysis were performed between 0 and 4 days of treatments. All Cd concentrations significantly reduced leaf area, fresh and dry weight, but leaf relative water contain only decreased with 200 and 300 µM Cd respect to control plants. Control and treated plants had similar soluble protein content and showed the same rate of soluble protein labeling under the assay conditions. Although protease activity increased with cadmium treatment, proteasome activity was significant inhibited respect to control values. Cadmium caused an increase of the ubiquitin-conjugated proteins and carbonyl groups content in treated leaves compared to control values. Cadmium induced an increase in protease specific activity, nevertheless it was not enough to avoid accumulation of oxidized proteins. These results suggest that 26S proteasome could be related to the secondary antioxidative defenses, degrading oxidized proteins in plant cells under oxidative stress generated by cadmium.