Expression of the Arabidopsis vacuolar H⁺‐pyrophosphatase gene (AVP1) improves the shoot biomass of transgenic barley and increases grain yield in a saline field

Abstract

SummaryCereal varieties with improved salinity tolerance are needed to achieve profitable grain yields in saline soils. The expression of AVP1, an Arabidopsis gene encoding a vacuolar proton pumping pyrophosphatase (H + -PPase), has been shown to improve the salinity tolerance of transgenic plants in greenhouse conditions. However, the potential for this gene to improve the grain yield of cereal crops in a saline field has yet to be evaluated. Recent advances in highthroughput nondestructive phenotyping technologies also offer an opportunity to quantitatively evaluate the growth of transgenic plants under abiotic stress through time. In this study, the growth of transgenic barley expressing AVP1 was evaluated under saline conditions in a pot experiment using nondestructive plant imaging and in a saline field trial. Greenhousegrown transgenic barley expressing AVP1 produced a larger shoot biomass compared to null segregants, as determined by an increase in projected shoot area, when grown in soil with 150 mM NaCl. This increase in shoot biomass of transgenic AVP1 barley occurred from an early growth stage and also in nonsaline conditions. In a saline field, the transgenic barley expressing AVP1 also showed an increase in shoot biomass and, importantly, produced a greater grain yield per plant compared to wild-type plants. Interestingly, the expression of AVP1 did not alter barley leaf sodium concentrations in either greenhouse-or field-grown plants. This study validates our greenhouse-based experiments and indicates that transgenic barley expressing AVP1 is a promising option for increasing cereal crop productivity in saline fields.

Arabidopsis Type I Proton-Pumping Pyrophosphatase Expresses Strongly in Phloem, Where It Is Required for Pyrophosphate Metabolism and Photosynthate Partitioning

“…A second batch of plants grown several months earlier gave similar cDNA expression and fresh weight values; *, P # 0.05; **, P # 0.01; and ***, P # 0.0001. Yang et al, 2007;Bao et al, 2008;Lv et al, 2008;Pasapula et al, 2011;Arif et al, 2013;Paez-Valencia et al, 2013;Schilling et al, 2014). Some of these transgenic plants also have enhanced rhizosphere acidification capacity and nutrient use efficiencies (Yang et al, 2007;Pei et al, 2012;Undurraga et al, 2012;Paez-Valencia et al, 2013;Li et al, 2014).…”

“…The salt-tolerant phenotype was explained by an increased capacity of Na + uptake into vacuoles, and the drought-resistance phenotype was attributed to an enhanced vacuolar osmoregulatory capacity (Gaxiola et al, 2001(Gaxiola et al, , 2002. Moreover, a study on the variation of salinity tolerance in Arabidopsis ecotypes reported a positive relationship between salt tolerance and AVP1 expression (Jha et al, 2010 Bao et al, 2008;Li et al, 2008;Pasapula et al, 2011;Schilling et al, 2014;Yang et al, 2014;R.A. Gaxiola, G.A.…”

“…Pizzio, and K. Regmi, unpublished data). In addition to salt and drought tolerance, increased shoot and root biomass and yield, enhanced root acidification, and improved nutrient use efficiencies were also reported (Yang et al, 2007(Yang et al, , 2014Lv et al, 2008;Pasapula et al, 2011;Pei et al, 2012;Arif et al, 2013;Paez-Valencia et al, 2013;Li et al, 2014;Schilling et al, 2014;Wang et al, 2014). These phenotypes are not well explained by the traditional model of type I H + -PPases operating solely on the vacuole to energize the tonoplast (Martinoia et al, 2007).…”

Job Sharing in the Endomembrane System: Vacuolar Acidification Requires the Combined Activity of V-ATPase and V-PPase

“…Moreover, the mild postgermination growth defect of fugu5 seedlings resulting in a slightly different cotyledon shape could be rescued by expression of a soluble yeast pyrophosphatase (Ferjani et al, 2011), highlighting a so far undiscovered role of the V-PPase in the removal of PP i required to avoid accumulation of inhibitory concentrations of PP i (Ferjani et al, 2012). These findings are also highly relevant as overexpression of AVP1 in Arabidopsis, as well as in a number of crop plants, results in improved drought and salt tolerance (Gaxiola et al, 2001;Pasapula et al, 2011;Gamboa et al, 2013;Schilling et al, 2014). AVP1 overexpression has also been reported to result in increased cell division at the onset of organ formation and increased auxin transport, which appeared to be a consequence of increased DpH PM (visualized as cytosolic alkalinization) resulting from altered distribution and abundance of the plasma membrane (PM) H + -ATPase and the PIN-FORMED1 auxin efflux facilitator .…”

Constitutive and Companion Cell-Specific Overexpression of AVP1, Encoding a Proton-Pumping Pyrophosphatase, Enhances Biomass Accumulation, Phloem Loading, and Long-Distance Transport

“…While the activity of an E. coli soluble PPase in the cytoplasm results in debilitated plants, overexpression of H + -PPases results in plants with greater salt and drought tolerance, improved nutrient uptake, and greater biomass accumulation (Li et al, , 2008(Li et al, , 2010Park et al, 2005;Yang et al, 2007;Bao et al, 2008;Lv et al, 2008Lv et al, , 2009Schilling et al, 2014). In Arabidopsis, ARABIDOPSIS VACUOLAR PYROPHOSPHATASE1 (AVP1) overexpression resulted in 40% to 60% greater leaf area and up to 8.4-fold increase in root growth, relative to the wild type Gonzalez et al, 2010).…”