The expression of the endogenous vacuolar Na+/H+ antiporters in roots and shoots correlates positively with the salt resistance of wheat (Triticum aestivum L.)

Among the most common effects of salinity is the growth inhibition by Na+ toxicity. Vacuolar Na+/H+ antiporters have been suggested to be involved in sequestering Na+ into vacuoles, thus preventing toxic effects of Na+ in the cytoplasm. This study reports how the expression of endogenous vacuolar Na+/H+ antiporters relates to the salt resistance of two wheat (Triticum aestivum L.) genotypes that differ in Na+ translocation from root to the shoot and Na' accumulation in the young and old leaves. The genotype SARC-1 having the lowest root-to-shoot Na+ translocation was the most salt-resistant in terms of absolute and relative shoot fresh weight production. However, compared to the saltsensitive wheat genotype 7-Cerros, the salt-resistant genotype SARC-1 showed a significantly higher Na+ concentration in young leaves, a similar Na+ concentration in medium leaves and a significantly lower Na+ concentration in the old leaves. The expression of endogenous vacuolar Na+/H+ antiporters in roots and shoots was significantly higher in the salt-resistant genotype SARC-1 than in the salt-sensitive genotype 7-Cerros. However, within a genotype there was little difference in the expression of vacuolar Na+/H+ antiporters between shoots and roots, and between cortical and stelar root parts. It is suggested that the higher expression of endogenous vacuolar Na+/H+ antiporters in roots and shoots of the salt-resistant wheat genotype SARC-1 facilitated Na' exclusion from the cytoplasm of its shoot cells and improved its salt resistance. (c) 2005 Elsevier Ireland Ltd. All rights reserved.