Soybean (Glycine max) yields are threatened by multiple stresses including soil salinity. GmSALT3 (a cation‐proton exchanger protein) confers net shoot exclusion for both Na⁺ and Cl⁻ and improves salt tolerance of soybean; however, how the ER‐localized GmSALT3 achieves this is unknown. Here, GmSALT3's function was investigated in heterologous systems and near isogenic lines that contained the full‐length GmSALT3 (NIL‐T; salt‐tolerant) or a truncated transcript Gmsalt3 (NIL‐S; salt‐sensitive). GmSALT3 restored growth of K⁺‐uptake‐defective Escherichia coli and contributed towards net influx and accumulation of Na⁺, K⁺ and Cl⁻ in Xenopus laevis oocytes, while Gmsalt3 was non‐functional. Time‐course analysis of NILs confirmed shoot Cl⁻ exclusion occurs distinctly from Na⁺ exclusion. Grafting showed that shoot Na⁺ exclusion occurs via a root xylem‐based mechanism; in contrast, NIL‐T plants exhibited significantly greater Cl⁻ content in both the stem xylem and phloem sap compared to NIL‐S, indicating that shoot Cl⁻ exclusion likely depends upon novel phloem‐based Cl⁻ recirculation. NIL‐T shoots grafted on NIL‐S roots contained low shoot Cl⁻, which confirmed that Cl⁻ recirculation is dependent on the presence of GmSALT3 in shoots. Overall, these findings provide new insights on GmSALT3's impact on salinity tolerance and reveal a novel mechanism for shoot Cl⁻ exclusion in plants.

中文翻译：

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大豆CHX型离子转运蛋白GmSALT3通过根衍生机制赋予叶片Na +排除，通过芽衍生过程赋予Cl-排除

大豆（Glycine max）的产量受到包括土壤盐分在内的多种胁迫的威胁。GmSALT3（阳离子质子交换蛋白）赋予两个娜净拍摄排阻⁺和Cl ^- ，提高了大豆的耐盐性; 但是，ER定位的GmSALT3如何实现这一点尚不清楚。在这里，在包含全长GmSALT3（NIL-T;耐盐）或截短的转录本Gmsalt3（NIL-S;对盐敏感）的异源系统和近等基因系中研究了GmSALT3的功能。GmSALT3恢复了K ⁺摄取缺陷型大肠杆菌的生长，并促进了净流入和Na ^+的积累，K ⁺和Cl ^-在非洲爪蟾卵母细胞，而Gmsalt3是无功能的。近等基因系的时程分析确认拍摄氯^-排斥娜明显发生⁺排斥。嫁接表明，芽的Na ⁺排斥是通过基于木质部的根部机制发生的。与此相反，NIL-T植物显著更大氯表现出^-在干木质部和韧皮部汁液相比NIL-S两个内容，指示拍摄氯^-排斥可能取决于新颖氯基于韧皮部^-再循环。嫁接在NIL‐S根上的NIL‐T枝条含有低的Cl ⁻，这证实了Cl⁻再循环取决于枝条中是否存在GmSALT3。总体而言，这些研究结果对GmSALT3对耐盐性的影响提供新的见解，并揭示了拍摄氯的新机制^-植物排斥。