Response of plasma membrane H+-ATPase to heavy metal stress in Cucumis sativus roots

Abstract

The effect of heavy metals on the modification of plasma membrane H+-ATPase (EC 3.6.3.14) activity in cucumber roots was studied. In plants stressed for 2 h with 10 μM or 100 μM Cd, Cu or Ni the hydrolytic as well as the transporting activity of H+-ATPase in the plasma membranes of root cells was decreased. Transcript levels of Cucumis sativus plasma membrane H+-ATPase in roots treated with 10 μM Cd, Cu, or Ni as well as with 100 μM Cu or Ni were similar to the control, indicating that the action of metals did not involve the gene expression level. Only in roots exposed to 100 μM Cd was the level of plasma membrane H+-ATPase mRNA markedly decreased. The inhibition of the plasma membrane proton pump caused by 100 μM Cd, Cu and Ni was partially diminished in the presence of cantharidin, a specific inhibitor of protein phosphatases. Western blot analysis with the antibody against phosphothreonine confirmed that decreased activity of plasma membrane H+-ATPase under heavy metals resulted from dephosphorylation of the enzyme protein. Taken together, these data strongly indicated that alteration of the enzyme under heavy metal stresses was mainly due to the post-translational modification of its proteins in short-term experiments.

Changes in pH and organic acids in mucilage of Eriophorum angustifolium roots after exposure to elevated concentrations of toxic elements

“…Cucumis sativus (Janicka-Russak et al 2008), sugar beet and wheat (Lindberg and Wingstrand, 1984;Lindberg et al 2004). In this context, it is likely that metal exposure results in a defense mechanism releasing organic anions from the plant roots.…”

Role of the plasma membrane H+-ATPase in the regulation of organic acid exudation under aluminum toxicity and phosphorus deficiency

“…41 Phosphorylation at the penultimate Thr residue of the plasma membrane H C -ATPase is a common example of post-translational modification altering the activity of this enzyme. 42 The association of 14-3-3 proteins with the phosphothreonine-containing sequence of the plasma membrane H C -ATPase maintains the phosphorylation state and results in its activation. 43,44 The 14-3-3 proteins, which are members of a highly conserved protein family with regulatory roles in all eukaryotes, interact with phosphorylated target proteins such as nitrate reductase, sucrose-phosphate synthase and plasma membrane H C -ATPase.…”

Copper and zinc affect the activity of plasma membrane H+-ATPase and thiol content in aquatic fungi

“…Accordingly, metal uptake in fungi is often reduced by a decrease in the extracellular pH [copper, Gadd & White (1985); zinc, Ross (1994)]. In plant roots, copper inhibited the hydrolytic activity of H + -ATPase (Burzynski & Kolano, 2003;Janicka-Russak et al, 2008). Protein phosphorylation depends on the energetic status of the cell, and metal exposure decreased the amount of the ATP in root tissues (Janicka-Russak et al, 2008).…”

“…In plant roots, copper inhibited the hydrolytic activity of H + -ATPase (Burzynski & Kolano, 2003;Janicka-Russak et al, 2008). Protein phosphorylation depends on the energetic status of the cell, and metal exposure decreased the amount of the ATP in root tissues (Janicka-Russak et al, 2008). This suggests that, in addition to the dephosphorylation intensity of the proton pump, the ATP level is an important factor in enzyme deactivation under metal stress.…”