CsICE1 and CsCBF1: two transcription factors involved in cold responses in Camellia sinensis.

C-repeat/dehydration-responsive element binding factors (CBFs) can induce the expression of a suite of cold-responsive genes to increase plant cold tolerance, and inducer of CBF expression 1 (ICE1) is a major activator for CBF. In the present study, we isolated the full-length cDNAs of ICE1 and CBF from Camellia sinensis, designated as CsICE1 and CsCBF1, respectively. The deduced protein CsICE1 contains a highly conserved basic helix-loop-helix (bHLH) domain and C-terminal region of ICE1-like proteins. CsCBF1 contains all conserved domains of CBFs in other plant species and can specifically bind to the C-repeat/dehydration-responsive element (CRT/DRE) as confirmed by electrophoretic mobility shift assay. The transcription of CsICE1 had no apparent alteration after chilling treatment (4°C). CsCBF1 expression was not detected in normal temperature (20°C) but was induced immediately and significantly by low temperature (4°C). Our results suggest that ICE1-CBF cold-response pathway is conserved in tea plants. CsICE1 and CsCBF1, two components of this pathway, play roles in cold responses in tea plants.