An Eggplant SmICE1a Gene Encoding MYC-type ICE1-like Transcription Factor Enhances Freezing Tolerance in Transgenic Arabidopsis Thaliana

Low temperature is a crucial environmental factor affecting the quality and production of eggplant. Therefore, it is necessary to explore the molecular mechanisms of low temperature response. We isolated an ICE (inducer of CBF expression) gene from Solanum melongena, named SmICE1a. We then analysed structure, transcriptional activity and expression patterns of SmICE1a. Moreover, we also expressed SmICE1a in Arabidopsis thaliana. Bioinformatics and expression analysis showed that SmICE1a has a typical S-rich motif, ZIP region, bHLH and ACT-like domain. The gene SmICE1a had transcriptional activity in yeast and was localized to the nucleus following transient expression in tobacco leaves, which suggests that SmICE1a is a transcription factor. A dual-LUC assay revealed that SmICE1a can enhance expression of SmCBF. Overexpression of SmICE1a in Arabidopsis increased freezing tolerance and caused multiple biochemical changes: transgenic lines have higher proline content and lower electrolyte leakage and malondialdehyde than the wild type in cold conditions. The expression of AtCBF and their target genes, AtCOR15A, AtCOR47, AtKIN1 and AtRD29A, were up-regulated in SmICE1a-overexpressing plants under low temperatures. Based on these results, we suggest that SmICE1a plays an important role in cold response, which may help to understand the cold response mechanism in eggplant and could be used to enhance cold tolerance of eggplant in future.