Plant Plasma Membrane H+-ATPase in Adaptation of Plants to Abiotic Stresses

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H+-ATPase is a major enzyme protein of the plant plasma membrane (PM). This protein belongs to a large superfamily of pumps termed P-type ATPases. A characteristic feature of P-ATPases is the formation of a phosphorylated intermediate during the catalytic cycle. Ptype ATPase genes can be divided into ten phylogenetic branches. Six of them are found in plants (Axelsen & Palmgren, 2001). The plasma membrane proton pump belongs to the P3type ATPase family. The H+-ATPase branch is subdivided into five subfamilies (Arango et al., 2003). Plasma membrane H+-ATPase is a tightly bound and integral transmembrane protein. The enzyme is a single polypeptide of ~100 kDa. By the use of the chemical energy of ATP, plasma membrane connected ATPases extrude protons from cells of plants to generate electrochemical proton gradients. The generation of this gradient has a major role in providing the energy for secondary active transport across the plasma membrane. The plant plasma membrane H+-ATPase is a proton pump which plays a central role in physiological functions such as nutrient uptake, intracellular pH regulation, stomatal opening and cell growth. Besides regulation of physiological processes, the plasma membrane proton pump also plays a role in adaptation of plants to changing conditions, especially stress conditions. Thus, H+-ATPase can be a mutual element for resistance mechanisms that are activated in various stress conditions. Many studies have shown the changes of gene expression of the plasma membrane H+-ATPase in response to a variety of environmental factors. Moreover, besides the genetic regulation of the proton pump, its activity may undergo fast post-translational modulation.