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Background and Aims <p>As a pioneer plant in saline soils, <i>Suaeda salsa</i> (L.) Pall. (<i>S. salsa</i>) exhibits exceptional salt tolerance and demonstrates substantial remediation potential in saline soil environments. Brassinosteroids (BRs) orchestrate plant growth, development, and stress adaptation, but the functional role of BRs biosynthetic genes and their role in salt tolerance of halophytes remains unclear. This study elucidates how <i>S. salsa</i> coordinates salt stress resilience via BRs biosynthesis, providing novel strategies for engineering salt-tolerant crops.</p> Methods <p>For plant transformation, <i>Arabidopsis thaliana</i> (L.) Heynh<i>.</i> (<i>Arabidopsis</i>) inflorescences were transformed using the floral-dip method, whereas <i>Nicotiana benthamiana</i> Domin (<i>N. benthamiana</i>) leaves, and <i>S. salsa</i> seedlings were infiltrated with <i>Agrobacterium</i> suspensions. Transformed tissues were histochemically assayed using GUS staining to quantify promoter responses to salt stress. Growth parameters (dry weight) and physiological indices including chlorophyll content, Na<sup>+</sup>/K<sup>+</sup> ion accumulation, BRs levels, and antioxidant enzyme activities/expression profiles were evaluated in <i>Arabidopsis</i> wild-type, overexpression lines, mutants, and complementation lines under differential salt treatments.</p> Results <p>Salinity markedly improved leaves BRs content and the expression of <i>SsBR6ox1</i> in <i>S. salsa.</i> Heterologous expression of <i>SsBR6ox1</i>, a halophyte-derived BRs biosynthesis gene with its native promoter conferring salt tolerance in <i>Arabidopsis</i>. Transgenic lines displayed improved root growth, elevated BRs levels, and enhanced Na<sup>+</sup>/K<sup>+</sup> homeostasis. Mechanistically, <i>SsBR6ox1</i> boosted antioxidant defenses, including peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) activities, thereby reducing oxidative damage and lipid peroxidation. Concurrently, it coordinately upregulating <i>AtSOS1</i> and other antioxidant genes, establishing a dual ion-efflux/ROS-scavenging axis. The promoter's stress-responsive <i>cis</i>-elements enable salt-inducible expression of <i>SsBR6ox1</i>.</p> Conclusion <p>Salt stress-induced upregulation of <i>SsBR6ox1</i> which elevates BRs levels, orchestrating a tripartite adaptation network through ion homeostasis enhancement, ROS scavenging capacity augmentation, and membrane stability maintenance, which collectively enhance root development and whole-plant salt tolerance.</p>

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Salt inducible promoter of Suaeda salsa SsBR6ox1 mediates brassinosteroids biosynthesis and salt tolerance in the halophytic species and transgenic Arabidopsis under salinity

  • 期刊论文

  • 发表日期：

    2026年3月30日

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  • Runtai Zhao,
  • Chaoran Shi,
  • Tong Wang,
  • Chenyang Li,
  • Yan Zhou,
  • Ruxin Zhao,
  • Lei Wang,
  • Jie Song

摘要

Background and Aims

As a pioneer plant in saline soils, Suaeda salsa (L.) Pall. (S. salsa) exhibits exceptional salt tolerance and demonstrates substantial remediation potential in saline soil environments. Brassinosteroids (BRs) orchestrate plant growth, development, and stress adaptation, but the functional role of BRs biosynthetic genes and their role in salt tolerance of halophytes remains unclear. This study elucidates how S. salsa coordinates salt stress resilience via BRs biosynthesis, providing novel strategies for engineering salt-tolerant crops.

Methods

For plant transformation, Arabidopsis thaliana (L.) Heynh. (Arabidopsis) inflorescences were transformed using the floral-dip method, whereas Nicotiana benthamiana Domin (N. benthamiana) leaves, and S. salsa seedlings were infiltrated with Agrobacterium suspensions. Transformed tissues were histochemically assayed using GUS staining to quantify promoter responses to salt stress. Growth parameters (dry weight) and physiological indices including chlorophyll content, Na+/K+ ion accumulation, BRs levels, and antioxidant enzyme activities/expression profiles were evaluated in Arabidopsis wild-type, overexpression lines, mutants, and complementation lines under differential salt treatments.

Results

Salinity markedly improved leaves BRs content and the expression of SsBR6ox1 in S. salsa. Heterologous expression of SsBR6ox1, a halophyte-derived BRs biosynthesis gene with its native promoter conferring salt tolerance in Arabidopsis. Transgenic lines displayed improved root growth, elevated BRs levels, and enhanced Na+/K+ homeostasis. Mechanistically, SsBR6ox1 boosted antioxidant defenses, including peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) activities, thereby reducing oxidative damage and lipid peroxidation. Concurrently, it coordinately upregulating AtSOS1 and other antioxidant genes, establishing a dual ion-efflux/ROS-scavenging axis. The promoter's stress-responsive cis-elements enable salt-inducible expression of SsBR6ox1.

Conclusion

Salt stress-induced upregulation of SsBR6ox1 which elevates BRs levels, orchestrating a tripartite adaptation network through ion homeostasis enhancement, ROS scavenging capacity augmentation, and membrane stability maintenance, which collectively enhance root development and whole-plant salt tolerance.