DlICE1, a stress-responsive gene from Dimocarpus longan, enhances cold tolerance in transgenic Arabidopsis

ICE1 (inducer of GBP expression 1) encodes a typical MYC-like basic helix-loop-helix (bHLH) transcription factor that acts as a pivotal component in the cold signalling pathway. In this study, DlICE1, a novel ICE1-like gene, was isolated from the southern subtropical fruit tree longan (Dimocarpus longan Lour.). DlICEI encodes a nuclear protein with a highly conserved bHLH domain. DlICEI expression was slightly upregulated under cold stress. Overexpression of DlICEI in Arabidopsis conferred enhanced cold tolerance via increased proline content, decreased ion leakage, and reduced malondialdehyde (MDA) and reactive oxygen species (ROS) accumulation. Expression of the ICE1-CBF cold signalling pathway genes, including AtCBF1/2/3 and cold-responsive genes (AtRD29A, AtCOR15A, AtCOR47 and AtKIN1), was also significantly higher in DlICEI-overexpressing lines than in wild-type (WT) plants under cold stress. In conclusion, these findings indicate that DlICE is a member of the bHLH gene family and positively regulates cold tolerance in D. longan.