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<p>Salt stress is a major constraint for legume productivity, and nitrogen (N) form is known to modulate plant stress responses. This study investigates how different N forms (nitrate, ammonium, and their combination) affect physiological, biochemical, and molecular responses of fenugreek (<i>Trigonella foenum-graecum</i>) under salinity, with focus on antioxidant defenses and nitrogen uptake mechanisms. Fenugreek plants were grown under controlled conditions with distinct N regimes, exposed or not to 100 mM NaCl. Membrane integrity was evaluated via malondialdehyde (MDA) and electrolyte leakage (EL). Antioxidant responses included enzymatic activities (CAT, GPX, APX) and non-enzymatic metabolites (phenolics, flavonoids, tannins, total antioxidant capacity). Stress-related phytohormones (ABA, salicylic acid, jasmonates), ion fluxes (NO₃⁻, NH₄⁺), total N content, and expression of nitrogen transporter genes (AMT1.1, NRT2.1) were analyzed. Ammonium-fed plants maintained membrane stability under salinity with lower MDA and EL and higher CAT and GPX activities. Non-enzymatic antioxidants and ABA/SA levels were elevated under NH₄⁺, whereas jasmonate accumulation was higher under mixed N. Gene expression showed upregulation of AMT1.1 with NH₄⁺ and NRT2.1 with NO₃⁻; mixed N induced divergent responses. NH₄⁺ uptake and AMT1.1 expression were strongly responsive to salinity, highlighting coordinated nitrogen assimilation and ROS detoxification. Nitrogen form critically influences fenugreek’s salt tolerance. NH₄⁺ enhances resilience by preserving membrane integrity, reinforcing antioxidant defenses, modulating hormonal balance, and regulating nitrogen transporters. Optimizing NH₄⁺ fertilization could improve salinity tolerance in fenugreek and other legumes.</p>

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Nitrogen Form Modulates NRT2.1 and AMT1.1 Transporters Genes Regulation and Antioxidant Defenses in Salt-Stressed Fenugreek Under Hydroponic Culture System

  • 期刊论文

  • 发表日期：

    2026年2月13日

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  • Mohamed Chebbi,
  • Hela Mahmoudi,
  • Leila Riahi,
  • Miguel Cerezo,
  • Zeineb Ouerghi

摘要

Salt stress is a major constraint for legume productivity, and nitrogen (N) form is known to modulate plant stress responses. This study investigates how different N forms (nitrate, ammonium, and their combination) affect physiological, biochemical, and molecular responses of fenugreek (Trigonella foenum-graecum) under salinity, with focus on antioxidant defenses and nitrogen uptake mechanisms. Fenugreek plants were grown under controlled conditions with distinct N regimes, exposed or not to 100 mM NaCl. Membrane integrity was evaluated via malondialdehyde (MDA) and electrolyte leakage (EL). Antioxidant responses included enzymatic activities (CAT, GPX, APX) and non-enzymatic metabolites (phenolics, flavonoids, tannins, total antioxidant capacity). Stress-related phytohormones (ABA, salicylic acid, jasmonates), ion fluxes (NO₃⁻, NH₄⁺), total N content, and expression of nitrogen transporter genes (AMT1.1, NRT2.1) were analyzed. Ammonium-fed plants maintained membrane stability under salinity with lower MDA and EL and higher CAT and GPX activities. Non-enzymatic antioxidants and ABA/SA levels were elevated under NH₄⁺, whereas jasmonate accumulation was higher under mixed N. Gene expression showed upregulation of AMT1.1 with NH₄⁺ and NRT2.1 with NO₃⁻; mixed N induced divergent responses. NH₄⁺ uptake and AMT1.1 expression were strongly responsive to salinity, highlighting coordinated nitrogen assimilation and ROS detoxification. Nitrogen form critically influences fenugreek’s salt tolerance. NH₄⁺ enhances resilience by preserving membrane integrity, reinforcing antioxidant defenses, modulating hormonal balance, and regulating nitrogen transporters. Optimizing NH₄⁺ fertilization could improve salinity tolerance in fenugreek and other legumes.