Exhibits cryoprotective activity toward stromal substrates in chloroplasts and in protoplasts and confers freezing tolerance to plants in a CBF-dependent manner. Protectant against various stresses (e.g. cold, drought and heat stress) by preventing protein aggregation and attenuating enzyme inactivation. Influences the intrinsic curvature of the inner membrane of the chloroplast envelope, and modulates the freeze-induced lamellar-to-hexagonal II phase transitions that occur in regions where the plasma membrane is brought into close apposition with the chloroplast envelope during freeze-induced osmotic contraction (By similarity). Mediates a shift in the melting curves of phospholipids-containing membranes to lower temperatures (PubMed:20510170). Involved in the regulation of leaf senescence by abscisic acid (ABA) in a VNI2-dependent manner (PubMed:21673078). Forms homooligomers which interact with potential stromal substrates in the stroma of chloroplasts (By similarity). Interacts with the galactose headgroup of the chloroplast lipid monogalactosyldiacylglycerol (MGDG) (PubMed:20510170). Strongly induced by cold (PubMed:8260628, PubMed:15144380, PubMed:12481097, PubMed:18808718). Accumulates in response to abscisic acid (ABA) (PubMed:8260628, PubMed:21673078). Accumulates during compatible but not during incompatible interactions with the downy mildew pathogen Hyaloperonospora arabidopsidis, and thus belongs to compatible specific (CS) proteins (PubMed:19656045). Predominantly unstructured in solution and mainly alpha-helical after drying. Belongs to the COR15 protein family. Truncated N-terminus.