What question did this study set out to answer?

This study aims to investigate the physiological and molecular mechanisms of active de-acclimation in winter wheat.

June 4, 2026Open Access

Mid-winter de-acclimation triggers a stress-like response in leaves of cold-acclimated wheat (Triticum aestivum L.) at the tillering stage

Key Points

This study aims to investigate the physiological and molecular mechanisms of active de-acclimation in winter wheat.
Phenotyping of eight wheat accessions with varying tolerance to freezing conditions.
RNA sequencing and gene ontology analyses to identify differentially expressed genes related to de-acclimation.
Expression analysis of hormone-related transcripts and validation via qPCR.
Tolerant accessions showed high survival rates and maintained photosynthetic efficiency after freezing versus susceptible lines that did not.
Distinct gene expression patterns were identified, with susceptible accessions having broader transcriptomic changes.
Key hormone pathways, particularly involving abscisic acid, were correlated with tolerance levels.

Abstract

Abstract Background Active de-acclimation, triggered by mid-winter warm spells, threatens winter wheat survival under freezing conditions. This study investigated the physiological and molecular mechanisms underlying the response to active de-acclimation in eight wheat accessions with contrasting tolerance levels. Results Phenotyping showed that tolerant accessions maintained high survival rates and photosynthetic efficiency after freezing in the de-acclimated state, whereas the same treatment was lethal to susceptible lines. Chlorophyll fluorescence parameters and principal component analysis clearly separated tolerant from sensitive accessions, indicating distinct genetic bases of freezing tolerance in cold-acclimated and de-acclimated states. RNA sequencing demonstrated that active de-acclimation is not merely the reversal of cold acclimation, as numerous genes were uniquely differentially expressed during this process. Susceptible accessions exhibited broader and more pronounced transcriptomic changes than tolerant ones, suggesting that tolerance involves a more controlled molecular response to warming. Gene ontology analyses showed enrichment of transcripts related to ethylene perception, hormone signalling, root development, and metal ion transport specifically associated with de-acclimation. Expression analysis and hormone profiling highlighted the role of abscisic acid (ABA), salicylic acid (SA), and selected cytokinins in differentiating tolerant and susceptible accessions. Notably, ABA hydroxylase expression and ABA levels were closely associated with tolerance. qPCR validation confirmed RNA-seq results for key hormone-related candidate genes. Conclusions Active de-acclimation in wheat is a complex response involving stress-related pathways, particularly hormone signalling. Cold acclimation capacity is critical for subsequent tolerance, and dual selection for freezing and de-acclimation tolerance is recommended in breeding programs. These findings identify ABA- and ethylene-related pathways as key targets for improving resilience to fluctuating winter temperatures.

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