A Na⁺/H⁺ Antiporter Gene from <i>Rosa multiflora</i> (<i>RmNHX2</i>) Functions in Salt Tolerance via Modulating ROS Levels and Ion Homeostasis

Abstract

High salinity restricts plant growth and geographic distribution. Plant intracellular Na+/H+ (NHX) antiporters have critical roles in plant development and stress response. However, the molecular functions of RmNHXs in Rosa multiflora remain unclear. In this study, we identified 11 putative RmNHXs in R. multiflora according to the genome-wide analysis. The RmNHXs were classified into three classes. Most of the RmNHXs were responsive to salt stress, with the greatest upregulation being observed in RmNHX2. RmNHX2 was localized at the tonoplast. RmNHX2 overexpression resulted in the enhanced salt tolerance in tobacco, whereas virus-induced gene silencing (VIGS) of RmNHX2 in R. multiflora elevated salt susceptibility. Under salt treatment, the transgenic tobaccos achieved less reactive oxygen species (ROS) accumulation and higher activities of antioxidant enzymes, which complied with the upregulated expressions of antioxidant genes. Moreover, RmNHX2-overexpression lines had a lower level of Na+, a higher level of K+, and a lower Na/K ratio. In contrast to the mentioned, VIGS of RmNHX2 in R. multiflora exhibited the opposite phenotype, accompanied by a compromised salt tolerance. Regarded together, these results demonstrate that RmNHX2 enhances plant salt tolerance by maintaining proper ion homeostasis, as well as by accelerating ROS scavenging.

Keywords

• <i>Rosa multiflora</i>
• <i>RmNHX2</i>
• salt tolerance
• ion homeostasis
• ROS scavenging