Cold-Induced Downregulation of TaSAP7-A2 Activates the TaCOLD1-2D-TaCML5-7B Module to Enhance Cold Tolerance in Wheat

Cold stress, including chilling and freezing, severely limits global wheat (Triticum aestivum L.) production. Although many cold-responsive genes have been identified, the mechanisms that connect early cold sensing to transcriptional regulation and downstream physiological adaptation are still not fully understood. By generating TaCOLD1-2D overexpression and CRISPR/Cas9 knockout lines in wheat and integrating protein interaction assays, transcriptional regulation analyses, physiological measurements, and haplotype analysis of 143 Chinese wheat accessions, we characterized the TaSAP7-A2/TaCOLD1-2D/TaCML5-7B regulatory module. TaSAP7-A2 functions as a transcriptional repressor that directly binds the TaCOLD1-2D promoter under normal conditions. Cold exposure rapidly downregulates TaSAP7-A2, relieving this repression and elevating TaCOLD1-2D expression. The increased TaCOLD1-2D then recruits TaCML5-7B in a Ca²⁺-dependent manner. This cascade activates ABA biosynthesis and signalling, promotes rapid stomatal closure, maintains ROS homoeostasis, and fine-tunes CBF-COR gene expression, conferring robust tolerance at both seedling and booting stages without affecting growth under non-stress conditions. A natural TaSAP7-A2 promoter haplotype (Hap-7A-2) with weakened repressive activity shows strong artificial selection in high-latitude cultivars. These results uncover an efficient derepression strategy that integrates early cold perception with Ca²⁺-ABA-mediated protective responses. The module provides valuable genetic targets for developing climate-resilient wheat while avoiding the growth penalties associated with constitutive defence activation.