Structure, Function, and Regulation of the Plasma Membrane Na+/H+ Antiporter Salt Overly Sensitive 1 in Plants

Abstract

Physiological studies have confirmed that export of Na+ to improve salt tolerance in plants is regulated by the combined activities of a complex transport system. In the Na+ transport system, the Na+/H+ antiporter salt overly sensitive 1 (SOS1) is the main protein that functions to excrete Na+ out of plant cells. In this paper, we review the structure and function of the Na+/H+ antiporter and the physiological process of Na+ transport in SOS signaling pathway, and discuss the regulation of SOS1 during phosphorylation activation by protein kinase and the balance mechanism of inhibiting SOS1 antiporter at molecular and protein levels. In addition, we carried out phylogenetic tree analysis of SOS1 proteins reported so far in plants, which implied the specificity of salt tolerance mechanism from model plants to higher crops under salt stress. Finally, the high complexity of the regulatory network of adaptation to salt tolerance, and the feasibility of coping strategies in the process of genetic improvement of salt tolerance quality of higher crops were reviewed.

Salinity-Induced Cytosolic Alkaline Shifts in Arabidopsis Roots Require the SOS Pathway

“…Among the several mechanisms known to convey salt tolerance, the ability to extrude cytosolic Na + is strongly correlated with salinity stress tolerance in different plant species [ 18 , 57 , 58 ]. This exclusion is mediated by the plasma membrane (PM) Na + /H + antiporter encoded by SALT OVERLY SENSITIVE 1 ( SOS1 ) gene and driven by the proton gradient generated by plasma membrane H + -ATPases [ 12 , 52 , 54 , 59 ].…”

“…Different signaling pathways are activated by salinity-induced Ca 2+ influx, among which the SOS pathway is paramount for salt tolerance [ 12 , 54 , 59 , 70 ]. The activity of SOS1 extrudes Na + in exchange for H + , which results in cytosolic acidification.…”

Regulation of Na+/H+ exchangers, Na+/K+ transporters, and lignin biosynthesis genes, along with lignin accumulation, sodium extrusion, and antioxidant defense, confers salt tolerance in alfalfa

“…The SOS pathway is recognized for salt stress signaling and tolerance plant system ( Almeida et al., 2017 ). SOS1 is a plasma membrane Na + /H + antiporter that regulates Na + extrusion from the cytoplasm and mediates long-distance (roots–shoots) Na + transport ( Xie et al., 2022 ). SOS2 , a serine/threonine protein kinase, activates the response of the plasma membrane Na + /H + antiporter SOS1 through phosphorylation ( Almeida et al., 2017 ).…”

“…SOS2 , a serine/threonine protein kinase, activates the response of the plasma membrane Na + /H + antiporter SOS1 through phosphorylation ( Almeida et al., 2017 ). SOS3 is a calcium sensor protein induced after salt stress–involving Ca 2+ signal and enhances the expression of SOS1 through the interaction of the SOS2–SOS3 kinase complex that leads to efflux of Na + from the cells ( Xie et al., 2022 ).…”

Variety-Specific Transcriptional and Alternative Splicing Regulations Modulate Salt Tolerance in Rice from Early Stage of Stress

“…Important roles of Na + and K + transporters for salt tolerance in rice has been discussed in many studies (Xie et al 2022). Increased activity of Na + transporters through either amino acid sequence changes or protein expression change that enduring relative low accumulation of Na + in the cytoplasm of cells could lighten the Na + toxicity and finally increase the salt tolerance of plants (Kobayashi et al 2017;Obata et al 2007;Oomen et al 2012;Ren et al 2005;Shen et al 2015).…”