The GPCR-type G protein, COLD1, of 455 aas and 9 TMSs in a 5 + 4 TMS arrangement. In cold tolerant cultivars (AC Q7X7S8) Met-187 is replaced by Lys-187. This polymorphism is associated with divergence in chilling tolerance of rice cultivars. COLD1 confers adaptation of japonica rice to chilling and originated from the Chinese wild populations of Oryza rufipogon (Ma et al. 2015).
Overexpression of COLD1(jap) significantly enhances chilling tolerance, whereas rice lines with a deficiency or downregulation of COLD1(jap) are sensitive to cold. COLD1 encodes a regulator of G-protein signaling that localizes to the plasma membrane and endoplasmic reticulum (ER). It interacts with the G-protein α subunit to activate the Ca²⁺ channel for sensing low temperature and to accelerate G-protein GTPase activity (Ma et al. 2015).