Expression Analysis of Genes Encoding NHX2 Antiporter and Subunit A of Vacuolar H+-ATPase Pump in Salt-Resistant and Salt-Sensitive Barley (Hordeum vulgare L.) Cultivars under Salt Stress

Abstract

Salinity is one of the most important factors causing limiting growth aspects. Salinity tolerance is a multigenic trait activating mechanisms such as high H+ pumping activity, like NHX2 that is a tonoplast localized Na+/H+ exchanger and actively transfers the excess sodium ions from the cytoplasm into the vacuole. Vacuolar (v-) H+-ATPase pump is also a tonoplast localized, providing the ATP energy required for tonoplast antiporters. Evaluation of the expression level of HvNHX2 and subunit A of v-H+-ATPase (VHA-A) genes using real-time RT-PCR, in root and shoot tissue of salt-sensitive Reihan and salt-tolerant Afzal barley (Hordeum vulgare L.) cultivars under different salinity concentrations indicated that increasing the concentrations or duration of NaCl stress would decrease the K+/Na ratio that is a signal for cascade responses to the stress but fluctuated expression level of studied genes in some time point. However, promoter analysis of studied genes showed that both have CAAT, TATA and W-box promoter motifs which involve pathogen, salt and ABA-responsive signaling pathways but differed in TC-rich repeats, A-box, TCA-element and GARE-motif that may be one of the reason of observed different.