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

VILCHEZ, ANA CAROLINA; MOLINERO, ROCÍO LUZ; VILLASUSO, ANA LAURA

JOURNAL OF PLANT BIOCHEMISTRY AND BIOTECHNOLOGY

SOC PLANT BIOCHEM BIOTECH

Año: 2026 vol. 34

0971-7811

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.