The ThCAP gene, which encodes a cold acclimation protein, was isolated from a Tamarix hispida NaCl-stress root cDNA library; its expression patterns were then assayed by qRT-PCR in different T. hispida tissues treated with low temperature (4 degrees C), salt (400 mM NaCl), drought (20% PEG6000) and exogenous abscisic acid (100 microM). Induction of ThCAP gene was not only responsive to different stress conditions but was also organ specific. When transgenic Populus (P. davidiana x P. bolleana) plants were generated, expressing ThCAP under regulation of the cauliflower mosaic virus CaMV 35S promoter, they had a greater resistance to low temperature than non-transgenic seedlings, suggesting that ThCAP might play an important role in cold tolerance.