Significance of the V-type ATPase for the adaptation to stressful growth conditions and its regulation on the molecular and biochemical level

Two electrogenic H+-pumps, the vacuolar type H+-ATPase (V-ATPase) and the v acuolar pyrophosphatase, coexist at membranes of the secretory pathway of p lants. The V-ATPase is the dominant H+-pump at endomembranes of most plant cells, both in terms of protein amount and, frequently, also in activity. T he V-ATPase is indispensable for plant growth under normal conditions due t o its role in energizing secondary transport, maintenance of solute homeost asis and, possibly, in facilitating vesicle fusion. Under stress conditions such as salinity, drought, cold, acid stress, anoxia, and excess heavy met als in the soil, survival of the cells depends strongly on maintaining or a djusting the activity of the V-ATPase. Regulation of gene expression and ac tivity are involved in adapting the V-ATPase on long- and short-term bases. The mechanisms known to regulate the V-ATPase are summarized in this paper with an emphasis on their implications for growth and development under st ress.