Drought- and salt-tolerant plants result from overexpression of the AVP1 H ⁺ -pump

Abstract

Transgenic plants overexpressing the vacuolar H ؉ -pyrophosphatase are much more resistant to high concentrations of NaCl and to water deprivation than the isogenic wild-type strains. These transgenic plants accumulate more Na ؉ and K ؉ in their leaf tissue than the wild type. Moreover, direct measurements on isolated vacuolar membrane vesicles derived from the AVP1 transgenic plants and from wild type demonstrate that the vesicles from the transgenic plants have enhanced cation uptake. The phenotypes of the AVP1 transgenic plants suggest that increasing the vacuolar proton gradient results in increased solute accumulation and water retention. Presumably, sequestration of cations in the vacuole reduces their toxic effects. Genetically engineered drought-and salt-tolerant plants could provide an avenue to the reclamation of farmlands lost to agriculture because of salinity and a lack of rainfall. S alt-and drought-tolerant plants maintain their turgor at low water potentials by increasing the number of solute molecules in the cell (1-3). The active transport of solutes depends on the proton gradients established by proton pumps. In plants, three distinct proton pumps generate proton electrochemical gradients across cell membranes. The P-type ATPase pumps cytoplasmic H Plant vacuoles constitute 40-90% of the total intracellular volume of a mature plant cell (5) and, in concert with the cytosol, generate the cell turgor responsible for growth and plant rigidity. Cell turgor depends on the activity of vacuolar H ϩ pumps that maintain the H ϩ electrochemical gradient across the vacuolar membrane, which permits the secondary active transport of inorganic ions, organic acids, sugars, and other compounds. The accumulation of these solutes is required to maintain the internal water balance (6).In principle, increased vacuolar solute accumulation could confer salt and drought tolerance. The sequestration of ions such as sodium could increase the osmotic pressure of the plant and at the same time reduce the toxic effects of this cation. Exposure to NaCl has been shown to induce the H ϩ transport activity of vacuolar pumps in both salt-tolerant (7, 8) and salt-sensitive plants (9). In principle, enhanced expression of either of the vacuolar proton pumps should increase the sequestration of ions in the vacuole by increasing the availability of protons. However, overexpression of the plant vacuolar H ϩ -ATPase would be difficult because it consists of many subunits, each of which would have to be overexpressed at the correct level in a single transgenic plant to achieve higher activity of the multisubunit complex (10). By contrast, the vacuolar H ϩ -pyrophosphatase of Arabidopsis is encoded by a single gene, AVP1 (11). AVP1 can generate a H Here we show that transgenic plants expressing higher levels of the vacuolar proton-pumping pyrophosphatase, AVP1, are more resistant to salt and drought than are wild-type plants. These resistance phenotypes are associated with increased internal stores of solutes. Materials and MethodsGe...

H+‐pyrophosphatase IbVP1 promotes efficient iron use in sweet potato [Ipomoea batatas (L.) Lam.]

“…Under stressful conditions, up‐regulation of enzyme expression enables plant cells to use PPi as an energy source and maintain membrane integrity and intracellular transport via hydrolysis‐mediated ion transport (Gaxiola et al ., 2016; Greenway and Gibbs, 2003; Stitt, 1998). Increased abiotic stress tolerance and enhanced growth performance in Pi or nitrogen deficiency were observed during H + ‐PPase overexpression in Arabidopsis (Gaxiola et al ., 2001), tomato(Dong et al ., 2011; Park et al ., 2005; Yang et al ., 2007), tobacco (Khoudi et al ., 2012), rice (Zhang et al ., 2011; Zhao et al ., 2006), maize (Li et al ., 2008), lettuce (Paez‐Valencia et al ., 2013) and cotton (Lv et al ., 2009; Pasapula et al ., 2011). Nevertheless, the role of H + ‐PPase‐induced Fe uptake is unknown.…”

Nitrogen Use Efficiency Is Mediated by Vacuolar Nitrate Sequestration Capacity in Roots of Brassica napus

“…The vacuole proton-pumps (V-ATPase and V-PPase) located in the tonoplast supply energy for active transport of NO 3 2 and accumulation within the vacuole (Gaxiola et al, 2001;Brüx et al, 2008;Krebs et al, 2010). Despite the fact about 90% of the volume of mature plant cells is occupied by vacuoles, vacuolar NO 3…”

“…However, this hypothesis needs to be substantiated. The mechanisms underlying both NO 3 2 short-distance (Gaxiola et al, 2001;De Angeli et al, 2006;Brüx et al, 2008;Krebs et al, 2010) and long-distance transport (Lin et al, 2008;Li et al, 2010) have been previously investigated, yet the underlying mechanisms regulating the flux of NO 3 2 and the obvious relationship between the two transport pathways, as well as their relation to NUE, are not well understood.…”

“…The NRT family of genes play a partial role in vacuolar NO 3 2 accumulation in petioles (Chiu et al, 2004) and seed tissues (Chopin et al, 2007), whereas the proton pumps and CLCa system in the tonoplast play a major role in accumulating NO 3 2 in vacuoles (Gaxiola et al, 2001;De Angeli et al, 2006;Brüx et al, 2008;Krebs et al, 2010). The vacuolar NO 3 2 short-distance transport system is spread throughout the plant tissues and is the principal means by which vacuolar NO 3 2 shortdistance transport and distribution is controlled (De Angeli et al, 2006;Krebs et al, 2010).…”

Salt Stress Signaling and Mechanisms of Plant Salt Tolerance

“…Salt stress induces tonoplast H + -ATPase and H + -PPase activities (69). Transgenic Arabidopsis plants overexpressing AVP1 (H + -PPase) showed enhanced sequestration of Na + into the vacuole and maintained higher relative leaf water content and enhanced salt and drought stress tolerance as compared with the wild type (70). NO-mediated signaling is implicated in the activation of plasma membrane H + -ATPase (71), but the regulators of tonoplast H + -ATPases and H + -PPase are yet to be identified.…”