Involved in chilling tolerance. Interacts with the G-protein alpha subunit GPA1 to activate the calcium channel for sensing low temperature and to accelerate G-protein GTPase activity. Interacts with GPA1/RGA1. No visible phenotype under normal growth conditions, but mutant plants are sensitive to cold. In cold sensitive indica cultivars (AC A2XX57) Lys-187 is replaced by Met-187 or Thr-187. These polymorphisms are 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. Belongs to the Golgi pH regulator (TC 1.A.38) family.