SOS1 is an electroneutral Na +/H + antiporter that belongs to the NhaP/SOS1 subfamily of the monovalent cation proton antiporter family 1 (CPA1) 14, 15. Thus, SOS1 has become an important target for the improvement of salinity resistance in agricultural biotechnology 12, 13. Overexpression of SOS1 has been shown to improve plant salt tolerance 10, whereas disruption of SOS1 expression conversely results in the loss of salt resistance in halophytes 11. Compared with the vacuolar Na +/H + transporters, SOS1 is insensitive to K + and plays a unique physiological role in cellular Na + homeostasis 8, 9.

SOS1, which is highly conserved in the phylae of the plant kingdom, is identified as the only Na +/H + transporter that localizes at the plasma membrane and specifically exports Na + by utilizing the electrochemical proton gradient generated by H +-ATPase 6, 7. Therefore, Na + extrusion from the cytosol is critical for the salt tolerance of plants, especially in saline soil 5. However, excessive accumulation of cytosolic Na + disrupts several important physiological processes, including the cell cycle, enzymatic reactions, and photosynthesis, and thus leads to stunted growth and arrested cell development 3, 4.

For most plants, low levels of Na + are beneficial for many processes, such as maintaining osmotic pressure, partly eliminating potassium deficiency symptoms, and stimulating plant growth 1, 2.

Sodium is one of the most abundant elements in Earth’s crust.

Dead space 3 plasma cutter model