DREB1/CBFs are key transcription factors involved in plant cold stress adaptation. The expression of DREB1/CBFs triggers a cold-responsive transcriptional cascade, after which many stress tolerance genes are expressed. Thus, elucidating the mechanisms of cold stress-inducible DREB1/CBF expression is important to understand the molecular mechanisms of plant cold stress responses and tolerance. We analyzed the roles of a transcription factor, ICE1 (INDUCER OF CBF EXPRESSION 1), that is well known as an important transcriptional activator in the cold-inducible expression of DREB1A/CBF3. ice1-1 is a widely accepted mutant allele known to abolish cold-inducible DREB1A expression, and this evidence has strongly supported ICE1-DREB1A regulation for many years. However, in ice1-1 outcross descendants, we unexpectedly discovered that ice1-1 DREB1A repression was genetically independent of the ice1-1 allele, ICE1(R236H). Moreover, neither ICE1 overexpression nor double loss-of-function mutation of ICE1 and its homologous SCRM2 altered DREB1A expression. Instead, a transgene locus harboring a reporter gene in the ice1-1 genome was responsible for altering DREB1A expression. The DREB1A promoter was hypermethylated due to the transgene. We showed that DREB1A repression in ice1-1 results from transgene-induced silencing and not genetic regulation by ICE1. The ICE1(R236H) mutation has also been reported as scrm-D, which confers constitutive stomatal differentiation. The scrm-D phenotype and the expression of a stomatal differentiation marker gene were confirmed to be linked to the ICE1(R236H) mutation. We propose that the current ICE1-DREB1 regulatory model should be revalidated without the previous assumptions.

DREB1 / CBFs是参与植物冷胁迫适应的关键转录因子。DREB1 / CBF的表达触发了冷应答转录级联反应，此后表达了许多胁迫耐受基因。因此，阐明冷胁迫诱导的DREB1 / CBF表达的机制对于理解植物冷胁迫反应和耐受性的分子机制很重要。我们分析了转录因子ICE1（CBF表达1的诱导物）的作用，众所周知，ICE1在DREB1A / CBF3的冷诱导表达中是重要的转录激活因子。ice1-1是一个广为接受的突变等位基因，已知它消除了冷诱导DREB1A的表达，这一证据强烈支持了ICE1-DREB1A监管已有多年。但是，在ice1-1异体后代中，我们意外地发现ice1-1 DREB1A抑制在基因上独立于ice1-1等位基因ICE1（R236H）。此外，无论是ICE1过表达也没有的双失功能突变ICE1及其同源SCRM2改变DREB1A表达。相反，在ice1-1基因组中具有报告基因的转基因基因座负责改变DREB1A的表达。由于转基因，DREB1A启动子被高度甲基化。我们证明了DREB1Aice1-1的抑制是转基因诱导的沉默引起的，而不是ICE1的遗传调控。ICE1（R236H）突变也被报道为scrm-D，它赋予气孔组成性分化。的SCRM-d表型和一个气孔分化标记基因的表达被证实被链接到ICE1（R236H）突变。我们建议应在没有先前假设的情况下重新验证当前的ICE1- DREB1监管模型。