The G protein-coupled receptor COLD1 promotes chilling tolerance in maize during germination

The geographic range and yield of the staple crop maize (Zea mays L.) are both strongly limited by low-temperature conditions. One of the most economical and effective measures for improvement of maize production is chilling tolerance enhancement. In this study, a chilling-tolerance gene in maize, ZmCOLD1, was cloned and characterized. This gene encodes a G protein-coupled receptor that is localized to the plasma membrane and the endoplasmic reticulum. A single nucleotide polymorphism (SNP) in ZmCOLD1, SNP2738, was found to confer chilling tolerance and to have promoted maize adaptations during speciation from teosinte. Overexpression of the excellent haplotype ZmCOLD1^Hap11 significantly enhanced chilling tolerance, whereas knocking down ZmCOLD1 increased sensitivity to low temperatures during the germination and seedling stages. ZmCOLD1 was associated with an influx of extracellular Ca²⁺, increases in abscisic acid content, and decreases in gibberellic acid and indole-3-acetic acid content under low temperatures during the germination stage. ZmCOLD1 interacted with the G protein α subunit ZmCT2 at the plasma membrane, and ZmCT2 interacted with ZmLanCL in the nucleus. These proteins are components of the chilling tolerance signaling pathway in maize that are triggered by abscisic acid and photosynthesis. These results offer novel strategies for improvement of chilling tolerance in key crop species.