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<p><i>Solanum scabrum</i> Mill. (huckleberry) is an important leafy vegetable that exhibits exclusion of Na⁺ from the leaf blade. This exclusion mechanism has previously been shown to involve the <i>S. scabrum</i> high-affinity K⁺ transporter (SsHKT). However, the involvement of other regulators, such as salt overly sensitive 1 (SOS1), remains unexplored. To elucidate the role of SOS1 in this exclusion mechanism, 21-day-old plants were exposed to control (0 mM NaCl) and saline (60 mM and 120 mM NaCl) conditions for 10 days in a hydroponic medium. Fresh weight (FW), dry weight (DW), and Na⁺ and K⁺ concentrations in the leaf, stem, and root were quantified. The cDNA of <i>SsSOS1</i> was isolated and heterologously expressed in the Na⁺-sensitive yeast strain AB11c, where it successfully complemented the Na⁺-sensitive phenotype of the mutant. Expression of <i>SsSOS1</i> enhanced growth of AB11c under salt stress. In parallel, the expression levels of <i>SsSOS1</i> and <i>SsHKT</i> were analyzed in the leaf, stem, and root tissues. Plant growth was not adversely affected by salinity stress. Under moderate salinity, Na⁺ concentrations in the root, stem, and leaf were 15, 29, and 4&#xa0;mg/g DW, respectively, increasing to 28, 40, and 7&#xa0;mg/g DW under high salinity. <i>SsHKT</i> expression was most pronounced in the root, showing 17-fold and 30-fold upregulation under moderate and high salinity, respectively. In contrast, <i>SsSOS1</i> expression was significantly upregulated only in the root under high salinity (24-fold), while it remained constitutively high and unchanged in the stem (&gt; 8-fold) across both stress levels. Notably, <i>SsSOS1</i> was also strongly induced (&gt; 4-fold) in the leaf under high salinity. These findings suggest that Na⁺ exclusion from the leaf blade is likely regulated synergistically by SsHKT and SsSOS1 in the root and stem. Under high salinity, a possible Na⁺ recirculation mechanism involving SsSOS1 in the leaf may further enhance this regulation. This coordinated regulation is likely important for salt stress adaptation and may represent a valuable trait for improving plant performance under saline conditions.</p>

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The Role of SOS1 and HKT Transporters in Na+ Exclusion in Huckleberry Under Saline Conditions

  • 期刊论文

  • 发表日期：

    2025年6月9日

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  • Dekoum V. M. Assaha,
  • Ahmad Mohammad M. Mekawy,
  • Liyun Liu,
  • Hirofumi Saneoka,
  • Akihiro Ueda

摘要

Solanum scabrum Mill. (huckleberry) is an important leafy vegetable that exhibits exclusion of Na⁺ from the leaf blade. This exclusion mechanism has previously been shown to involve the S. scabrum high-affinity K⁺ transporter (SsHKT). However, the involvement of other regulators, such as salt overly sensitive 1 (SOS1), remains unexplored. To elucidate the role of SOS1 in this exclusion mechanism, 21-day-old plants were exposed to control (0 mM NaCl) and saline (60 mM and 120 mM NaCl) conditions for 10 days in a hydroponic medium. Fresh weight (FW), dry weight (DW), and Na⁺ and K⁺ concentrations in the leaf, stem, and root were quantified. The cDNA of SsSOS1 was isolated and heterologously expressed in the Na⁺-sensitive yeast strain AB11c, where it successfully complemented the Na⁺-sensitive phenotype of the mutant. Expression of SsSOS1 enhanced growth of AB11c under salt stress. In parallel, the expression levels of SsSOS1 and SsHKT were analyzed in the leaf, stem, and root tissues. Plant growth was not adversely affected by salinity stress. Under moderate salinity, Na⁺ concentrations in the root, stem, and leaf were 15, 29, and 4 mg/g DW, respectively, increasing to 28, 40, and 7 mg/g DW under high salinity. SsHKT expression was most pronounced in the root, showing 17-fold and 30-fold upregulation under moderate and high salinity, respectively. In contrast, SsSOS1 expression was significantly upregulated only in the root under high salinity (24-fold), while it remained constitutively high and unchanged in the stem (> 8-fold) across both stress levels. Notably, SsSOS1 was also strongly induced (> 4-fold) in the leaf under high salinity. These findings suggest that Na⁺ exclusion from the leaf blade is likely regulated synergistically by SsHKT and SsSOS1 in the root and stem. Under high salinity, a possible Na⁺ recirculation mechanism involving SsSOS1 in the leaf may further enhance this regulation. This coordinated regulation is likely important for salt stress adaptation and may represent a valuable trait for improving plant performance under saline conditions.