Comparative study of free amino acids at metabolite and gene expression levels in Triticeae during cold acclimation

This study investigates the freezing tolerance and cold-induced changes in amino acid metabolism in three Triticeae species (rye, wheat, and barley) with varying levels of freezing tolerance. Freezing tests confirmed that rye exhibited the highest tolerance, while barley showed the highest sensitivity. Cold acclimation significantly increased total free amino acid levels, with wheat and barley showing nearly twice the accumulation compared to rye. The glutamate family of amino acids, particularly proline (Pro), γ-aminobutyric acid (GABA), and glutamine (Gln), displayed substantial increase during cold treatment. Pro levels were notably higher in freezing-tolerant wheat and barley genotypes, suggesting its role in osmotic stress mitigation. However, this correlation was absent in rye. Gene expression analysis revealed that cold-induced proline accumulation is likely regulated at the post-transcriptional level, particularly involving the P5CS gene. These findings highlight the species-specific metabolic adjustments and regulatory mechanisms underlying freezing tolerance in Triticeae species, emphasizing the central role of proline and glutamate family amino acids in cold acclimation.