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<p>Chilling stress is a significant constraint on the growth and productivity of many crops. Pre-exposing seedlings to mild chilling stress—a strategy known as stress-specific priming—can enhance their tolerance to subsequent cold conditions. In this study, we investigated how such pre-exposure affects proline (Pro) metabolism in barley (<i>Hordeum vulgare</i> L.) seedlings subjected to chilling stress. Seedlings primed through prior exposure exhibited significantly higher levels of free Pro (2 ± 0.01&#xa0;mol/g.FW), particularly in the roots, where this accumulation was associated with increased biosynthesis (40 ± 1%), reduced degradation (25 ± 2%), and decreased lipid peroxidation. In leaves, elevated Pro (1 ± 0.01&#xa0;mol/g.FW) levels appeared to result from translocation rather than local synthesis, as changes were independent of Δ¹-pyrroline-5-carboxylate synthetase (P5CS) activity. Gene expression analysis showed that pre-exposure upregulated <i>P5CS</i>, <i>ProDH</i> (proline dehydrogenase), and <i>DFR1</i> (drought and freezing responsive gene 1), while <i>OAT</i> (ornithine δ-aminotransferase) remained unchanged, suggesting limited involvement of the OAT pathway. These findings reveal that chilling pre-exposure reprograms proline metabolism in barley roots, contributing to improved cold tolerance and offering insights into stress adaptation mechanisms in plants.</p>

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Pre-exposure to chilling stress enhances proline-mediated cold tolerance in barley seedling roots via metabolic modulation

  • 期刊论文

  • 发表日期：

    2026年1月17日

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  • Ana Carolina Vilchez,
  • Rocío Luz Molinero,
  • Ana Laura Villasuso

摘要

Chilling stress is a significant constraint on the growth and productivity of many crops. Pre-exposing seedlings to mild chilling stress—a strategy known as stress-specific priming—can enhance their tolerance to subsequent cold conditions. In this study, we investigated how such pre-exposure affects proline (Pro) metabolism in barley (Hordeum vulgare L.) seedlings subjected to chilling stress. Seedlings primed through prior exposure exhibited significantly higher levels of free Pro (2 ± 0.01 mol/g.FW), particularly in the roots, where this accumulation was associated with increased biosynthesis (40 ± 1%), reduced degradation (25 ± 2%), and decreased lipid peroxidation. In leaves, elevated Pro (1 ± 0.01 mol/g.FW) levels appeared to result from translocation rather than local synthesis, as changes were independent of Δ¹-pyrroline-5-carboxylate synthetase (P5CS) activity. Gene expression analysis showed that pre-exposure upregulated P5CS, ProDH (proline dehydrogenase), and DFR1 (drought and freezing responsive gene 1), while OAT (ornithine δ-aminotransferase) remained unchanged, suggesting limited involvement of the OAT pathway. These findings reveal that chilling pre-exposure reprograms proline metabolism in barley roots, contributing to improved cold tolerance and offering insights into stress adaptation mechanisms in plants.