Copper mediated inhibition on protein synthesis in rice shoots

Abstract

Recently several claims of copper (Cu) contamination in the lower reaches of the Sado River in the Alcacer do Sal region of Portugal (a major rice producing area) have been reported. In an attempt to study the effect of excess Cu on protein contents without anthropogenic interventions (amendments with fertilizers and sludges, application of pesticides, etc.), rice (Oryza sativa L.) plants were grown for one month in nutrient solutions containing Cu concentrations ranging from 0.002 to 6.25 mg/L. In order to understand the mechanism responsible for the observed decline of protein content with increasing Cu levels, the membrane permeability as well as the acid RNAse and protease activities were investigated. It was found that the membrane permeability and the acid RNAse activity increased with increasing Cu concentration. An increase in the protease activity was also observed, but only at the two highest Cu treatments. The effects of increasing Cu levels on protein contents are discussed on the basis of the measured acid RNAse and protease activities. The data is also discussed by considering the Cu contamination in the lower reaches of the Sado River.