Advances in the Molecular Regulatory Network of Low-Temperature Tolerance in Maize: Key Genes, Hormones, Signaling Pathways, and Genetic Improvement Strategies

Maize (Zea mays L.) is a globally important crop, but its sensitivity to cold stress leads to substantial yield losses in temperate zones, where low temperatures, particularly below 10 °C, critically constrain cultivation in high-altitude and high-latitude regions. Recent progress has identified key cold-tolerance genes, dissected natural variations, elucidated signaling pathways, and enabled multi-omics network construction. Some studies have provided evidence for the proposed coupling of ZmICE1 with amino acid metabolism and COR gene expression, the association of COOL1 promoter variation with HY5 binding and high-latitude adaptation, and the involvement of HSF21 in lipid homeostasis without an apparent yield penalty. Several novel genes (ZmWAK3, ZmMAPK4, TIP4;3, ZmDUF966-10) have been identified as promising candidates, expanding the genetic reservoir for further validation. Mechanistically, an unconventional ZmBSK4-ZmMAPK4 cascade, calcium-MAPK crosstalk, histone modifications, and small RNA-mediated regulation have been implicated in cold responses, although the extent to which each mechanism has been experimentally validated varies. Integrative approaches (chromatin accessibility, WGCNA, multi-omics) have revealed hierarchical synergies among transcription factors, epigenetics, hormones, and metabolism. Favorable alleles (COOL1HapA, HSF21Hap1, and the TIP4;3 beneficial haplotype) represent potential targets for molecular design, while CRISPR/Cas9 offers opportunities to accelerate gene editing and pyramiding. This review synthesizes these advances, and offers a comprehensive framework for cold-tolerance breeding in maize.