Agarwal Manu, Hao Yujin, Kapoor Avnish, Dong Chun-Hai, Fujii Hiroaki, Zheng Xianwu, Zhu Jian-Kang
Institute for Integrative Genome Biology and Department of Botany & Plant Science, University of California, Riverside, California 92521, USA.
J Biol Chem. 2006 Dec 8;281(49):37636-45. doi: 10.1074/jbc.M605895200. Epub 2006 Oct 2.
Cold temperatures trigger the expression of the CBF family of transcription factors, which in turn activate many downstream genes that confer freezing tolerance to plants. It has been shown previously that the cold regulation of CBF3 involves an upstream bHLH-type transcription factor, ICE1. ICE1 binds to the Myc recognition sequences in the CBF3 promoter. Apart from Myc recognition sequences, CBF promoters also have Myb recognition sequences. We report here that the Arabidopsis MYB15 is involved in cold-regulation of CBF genes and in the development of freezing tolerance. The MYB15 gene transcript is up-regulated by cold stress. The MYB15 protein interacts with ICE1 and binds to Myb recognition sequences in the promoters of CBF genes. Overexpression of MYB15 results in reduced expression of CBF genes whereas its loss-of-function leads to increased expression of CBF genes in the cold. The myb15 mutant plants show increased tolerance to freezing stress whereas its overexpression reduces freezing tolerance. Our results suggest that MYB15 is part of a complex network of transcription factors controlling the expression of CBFs and other genes in response to cold stress.
低温会触发转录因子CBF家族的表达，而CBF家族反过来又会激活许多赋予植物抗冻性的下游基因。先前的研究表明，CBF3的冷调控涉及上游的bHLH型转录因子ICE1。ICE1与CBF3启动子中的Myc识别序列结合。除了Myc识别序列外，CBF启动子还含有Myb识别序列。我们在此报告，拟南芥MYB15参与了CBF基因的冷调控以及抗冻性的形成。MYB15基因转录本受冷胁迫上调。MYB15蛋白与ICE1相互作用，并与CBF基因启动子中的Myb识别序列结合。MYB15的过表达导致CBF基因表达降低，而其功能缺失则导致CBF基因在低温下表达增加。myb15突变体植株对冻害胁迫的耐受性增强，而过表达则降低了抗冻性。我们的结果表明，MYB15是一个复杂转录因子网络的一部分，该网络控制着CBF和其他基因在冷胁迫下的表达。
