Overexpression of the Nitraria sibirica Pall. H-pyrophosphatase gene NsVP1 improves Arabidopsis salt tolerance.

Nitraria sibirica Pall., a perennial euhalophytic dwarf shrub, exhibits exceptional salt tolerance and serves as an ideal model species for saline-alkali land remediation, identification of novel salt-responsive genes, and deciphering molecular mechanisms underlying halophytic adaptation. Our previous investigations have shown that salt stress significantly upregulates both the expression and enzymatic activity of vacuolar H-pyrophosphatase (H-PPase) in this species. However, the detailed functional specificity of H-PPase in N. sibirica remains poorly characterized. Here, we cloned and functionally characterized NsVP1, a tonoplast-localized type I H-PPase from N. sibirica. Quantitative real-time PCR (RT-qPCR) analysis revealed that 400 mM NaCl treatment induced significant upregulation of NsVP1 expression, resulting in 6.6-fold and 29.7-fold increases in stems and leaves, respectively. Functional characterization studies demonstrated that NsVP1 overexpression in Arabidopsis conferred enhanced salinity tolerance through multifaceted regulatory mechanisms: (1) promoted vacuolar compartmentalization and Na exclusion via upregulated vacuolar H-PPase activity and synergistic interactions with NHX1 and SOS1, (2) decreased K loss and maintained cytosolic K/Na homeostasis, and (3) improved reactive oxygen species scavenging capacity. Notably, the succulent stem and leaf tissues of N. sibirica may enhance its ability to compartmentalize Na, contributing to its superior salt tolerance.

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