Differential regulation of vacuolar H+-ATPase and H+-PPase in Cucumis sativus roots by zinc and nickel

▶ Zinc and nickel visibly inhibit the activities of V-ATPase in cucumber roots whereas activities of V-PPase are modified to a lesser extent. ▶ Changes in the activities of both tonoplast proton pumps in response to Zn and Ni were not due to the modification in the expression of CsVHA-A, CsVHA-c and CsVP genes encoding V-ATPase subunit A and c, and V-PPase, respectively. ▶ V-ATPase seems not to play any essential role in zinc and nickel tolerance in cucumber plants. ▶ Pyrophosphatase appears to be sufficient to maintain both an electrochemical proton gradient across the tonoplast and active vacuolar accumulation under zinc and nickel stress.