Redox dependence of transport activity of tonoplast proton pumps: Effects of nitric oxide exposure during ontogenesis and under hypoosmotic and hyperosmotic stress

Abstract

Variations of the redox status is shown to inhibit the transport activity of tonoplast proton pumps at different stages of ontogenesis and under the conditions of hyperosmotic stress. However, the activity of H+-ATPase increased by 60% under hypoosmotic stress in the presence of GSH. The influence of nitric oxide on the transport activity of tonoplast proton pumps also depended on the redox status. In the case of change of the redox status, stimulating effect of nitric oxide turned inhibitory, except for simultaneous application of hypoosmotic stress and nitric oxide. In this case, stimulation of both proton pumps was observed and the activity of H+-ATPase increased in the presence of GSH, though the activity of H+-PPase increased in the presence of GSSG. This may explain the necessity of the presence in the vacuolar membrane of two proton pumps having similar functions.