Overexpression of a heading Chinese cabbage ICE1 gene confers freezing tolerance in transgenic rice

Low temperature stress operates the ICE1-CBF cold-responsive signal pathway of plants, which leads to the overexpression of a series of genes to enhance freezing tolerance. In this study, a novel MYC-type ICE1-like gene, BcICE1, was isolated from heading Chinese cabbage (Brassica campestris ssp. Pekinensis Lour. Olsson), and its function in freezing tolerance was characterized in rice. The expression of BcICE1 gene was constitutive with higher transcriptional levels in stems and leaves than in roots. The low temperature, ABA and NaCl treatments could significantly up-regulate BcICE1 expression levels, but dehydration stress had less effect on its expression. Under low temperature stress, the rice lines overexpressing BcICE1 gene enhanced freezing tolerance according to higher survival rate, higher accumulation of soluble sugars and proline, a remarkable decline in electrolyte leakage rate and MDA levels, and higher chlorophyll content compared with non-transgenic plants. As downstream cold-regulated genes, the expression levels of OsDREB1B, OsTPP1, J013091D15 and J023041L05 were obviously up-regulated in rice overexpressing BcICE1 under low temperature stress, suggesting BcICE1 was dependent of a CBF/DREB1 cold-responsive pathway. In short, above data showed that BcICE1 had a positive effect on improving rice freezing tolerance, which most likely result from the up-regulation of OsDREB1B, OsTPP1, J013091D15 and J023041L05 expression levels by interaction with the BcICE1 gene under low temperature stress.