Cucumber (Cucumis sativus L.) over-expressing cold-induced transcriptome regulator ICE1 exhibits changed morphological characters and enhances chilling tolerance

Cold is an environmental factor that limits the growing season of cucumber and adversely affects fruit quality and productivity. ICE1 is a positive regulator of CBF3 and has a critical role in cold stress ( Chinnusamy et al., 2003). To test the function and potential use of cold-induced transcriptome regulator ICE1 (inducer of CBF expression) in improving the chill tolerance of cucumbers, the Arabidopsis ICE1 gene driven by super promoter was introduced into cucumbers by Agrobacterium-mediated transformation. Transgenic plants were obtained, and were confirmed by PCR and southern blot, then the expression of ICE1 was tested by RT-PCR. Transgenic plants exhibited dwarf phenotypes, and shorter internodes, with higher nodes in the first female flowers and a lower female flower rate of every node than wild type plants. Under cold stress, the chilling index of four transgenic lines (IF3, IF6, IF7, and IF10) was decreased significantly, indicating their improved chilling tolerance. Over-expression of ICE1 in cucumbers could induce the expression of cold-responsive genes, further activating the accumulation of soluble sugars and free proline, and inhibiting malondialdehyde (MDA) accumulation. This leads to electrolyte leakage and regulation of osmotic potential to osmotic stress under cold stress.