Switchgrass () is a warm-season perennial grass. Improving its cold tolerance is important for its sustainable production in cooler regions. Through genome-wide bioinformatic analysis of switchgrass - genes (), we found that several , including , might play regulatory roles in plant cold tolerance. The objectives of this study were to characterize using reverse genetics approach and to understand its functional role in cold signal transduction and cold tolerance in switchgrass. is an intronless gene encoding a transcriptional activation factor. The expression of was rapidly and highly induced by cold stress. Transgenic switchgrass with over-expressed driven under maize ubiquitin promoter showed significantly improved chilling tolerance at 4 °C as demonstrated by less electrolyte leakage and higher relative water content than wild-type (WT) plants, as well as significantly higher survival rate after freezing treatment at - 5 °C. Improved cold tolerance of transgenic lines was associated with significantly up-regulated expression of -- regulon and ABA-responsive genes during cold treatment. was the first characterized switchgrass cold-tolerance gene and also the only - family gene known as a transcription factor in plant cold tolerance. PvC3H72 was an added signaling component in plant cold tolerance associated with regulation of ICE1-CBF-COR regulon and ABA-responsive genes. Knowledge gained in this study not only added another acting component into plant cold-tolerance mechanism, but also be of high value for genetic improvement of cold tolerance in switchgrass as well as other warm-season grasses.