A Golgi-Localized Sodium/Hydrogen Exchanger Positively Regulates Salt Tolerance by Maintaining Higher K+/Na+ Ratio in Soybean

Salt stress caused by soil salinization, is one of the main factors that reduce soybean yield and quality. A large number of genes have been found to be involved in the regulation of salt tolerance. In this study, we characterized a soybean sodium/hydrogen exchanger gene <i>GmNHX5</i> and revealed its functional mechanism involved in the salt tolerance process in soybean. <i>GmNHX5</i> responded to salt stress at the transcription level in the salt stress-tolerant soybean plants, but not significantly changed in the salt-sensitive ones. GmNHX5 was located in the Golgi apparatus, and distributed in new leaves and vascular, and was induced by salt treatment. Overexpression of <i>GmNHX5</i> improved the salt tolerance of hairy roots induced by soybean cotyledons, while the opposite was observed when <i>GmNHX5</i> was knockout by CRISPR/Cas9. Soybean seedlings overexpressing <i>GmNHX5</i> also showed an increased expression of <i>GmSOS1</i>, <i>GmSKOR</i>, and <i>GmHKT1</i>, higher K⁺/Na⁺ ratio, and higher viability when exposed to salt stress. Our findings provide an effective candidate gene for the cultivation of salt-tolerant germplasm resources and new clues for further understanding of the salt-tolerance mechanism in plants.