Aluminum increases phosphorylation of particular proteins in cellular suspension cultures of coffee (Coffea arabica)

Aluminum (Al) is the most abundant metal in the earthʹs crust and occurs in a number of different forms in the soil. Al toxicity is a global problem that limits crop productivity in acid soils. Coffee is a plant which grows in soils with a high organic matter content, and Al is available in these soils because they are acidic. In the present work, we demonstrate the effect of aluminum toxicity on the phosphorylation pattern of proteins. Coffea arabica suspension cells were incubated with increasing concentrations of AlCl3 (200-1000 μmol/L), and an in vitro phosphorylation reaction with cell extracts was performed. There was no change in the proteins present in extracts from cells treated with AlCl3, compared with untreated cells. However, the protein phosphorylation patterns did change. The phosphorylated proteins with a molecular mass of 18, 31 and 53 kDa increased dramatically after in vivo treatment of cells with AlCl3. When AlCl3 was added to the reaction mixture, no differences in phosphorylation patterns were observed. These results suggest that in vivo treatment of Coffea cells with AlCl3 affects the activity of some protein kinases.