The State Key Laboratory of Crop Biology, National Research Center for Apple Engineering and Technology, College of Horticulture Science and Engineering, Shandong Agricultural University, Tai-An, Shandong 271018, China.
BMC Plant Biol. 2012 Feb 15;12:22. doi: 10.1186/1471-2229-12-22.
Plant growth is greatly affected by low temperatures, and the expression of a number of genes is induced by cold stress. Although many genes in the cold signaling pathway have been identified in Arabidopsis, little is known about the transcription factors involved in the cold stress response in apple.
Here, we show that the apple bHLH (basic helix-loop-helix) gene MdCIbHLH1 (Cold-Induced bHLH1), which encodes an ICE-like protein, was noticeably induced in response to cold stress. The MdCIbHLH1 protein specifically bound to the MYC recognition sequences in the AtCBF3 promoter, and MdCIbHLH1 overexpression enhanced cold tolerance in transgenic Arabidopsis. In addition, the MdCIbHLH1 protein bound to the promoters of MdCBF2 and favorably contributed to cold tolerance in transgenic apple plants by upregulating the expression of MdCBF2 through the CBF (C-repeat-binding factor) pathway. Our findings indicate that MdCIbHLH1 functions in stress tolerance in different species. For example, ectopic MdCIbHLH1 expression conferred enhanced chilling tolerance in transgenic tobacco. Finally, we observed that cold induces the degradation of the MdCIbHLH1 protein in apple and that this degradation was potentially mediated by ubiquitination and sumoylation.
Based on these findings, MdCIbHLH1 encodes a transcription factor that is important for the cold tolerance response in apple.
植物生长受低温影响较大，许多基因的表达受冷胁迫诱导。尽管拟南芥中已鉴定出许多冷信号通路中的基因，但苹果中参与冷胁迫反应的转录因子知之甚少。
本研究表明，苹果 bHLH（碱性螺旋-环-螺旋）基因 MdCIbHLH1（冷诱导 bHLH1）对冷胁迫有明显的诱导作用。MdCIbHLH1 蛋白特异性结合 AtCBF3 启动子中的 MYC 识别序列，过表达 MdCIbHLH1 可增强转基因拟南芥的耐寒性。此外，MdCIbHLH1 蛋白与 MdCBF2 的启动子结合，通过 CBF（C 重复结合因子）途径上调 MdCBF2 的表达，有利于转基因苹果植株的耐寒性。研究结果表明，MdCIbHLH1 在不同物种中参与胁迫耐受。例如，异位表达 MdCIbHLH1 可赋予转基因烟草增强的抗冷性。最后，我们观察到冷胁迫诱导苹果中 MdCIbHLH1 蛋白的降解，这种降解可能是通过泛素化和 SUMO 化介导的。
基于这些发现，MdCIbHLH1 编码一个转录因子，对苹果的耐寒性反应很重要。
