NaCl-induced expression of AtVHA-c5 gene in the roots plays a role in response of Arabidopsis to salt stress

Suppression of AtVHA-c5 expression results in changes in H+ and Na+ fluxes of roots, and increase sensitivity to salt in Arabidopsis. Vacuolar-type H+-ATPase (V-ATPase), a multisubunit endomembrane proton pump, is essential in plant growth and response to environmental stresses. In the present study, the function of Arabidopsis V-ATPase subunit c5 (AtVHA-c5) gene in response to salt stress was investigated. Subcellular localization showed that AtVHA-c5 was mainly localized to endosomes and the vacuolar membrane in Arabidopsis. The analysis of quantitative real-time PCR showed that expression of AtVHA-c5 gene was induced by NaCl stress. Histochemical analysis revealed that AtVHA-c5 was expressed in the root epidermis of untreated Arabidopsis and in the whole root elongation zone after NaCl treatment. Phenotypic analysis showed that the atvha-c5 mutant is sensitive to high NaCl as compared to the wild type. The non-invasive micro-test technology measurement demonstrated that the net H+ and Na+ efflux in the root elongation zone of the atvha-c5 mutant was weaker than that of the wild type under NaCl treatment, suggesting that H+ and Na+ fluxes in atvha-c5 roots are impaired under NaCl stress. Moreover, compared to the wild type, the expression of AtSOS1 (salt overly sensitive 1) and AtAHA1 (plasma membrane H+-ATPase 1) were down-regulated in atvha-c5 roots under NaCl stress. Overall, our results indicate that AtVHA-c5 plays a role in Arabidopsis root response to NaCl stress by influencing H+ and Na+ fluxes.