Dhillon Taniya, Morohashi Kengo, Stockinger Eric J
Department of Horticulture and Crop Science, The Ohio State University/Ohio Agricultural Research and Development Center (OARDC), Wooster, OH, 44691, USA.
Center for Applied Plant Sciences, The Ohio State University, Columbus, OH, 43210, USA.
Plant Mol Biol. 2017 Jun;94(3):333-347. doi: 10.1007/s11103-017-0610-z. Epub 2017 Apr 22.
The C-Repeat Binding Factors (CBFs) are DNA-binding transcriptional activators that were identified using Arabidopsis thaliana. In barley, Hordeum vulgare, a cluster of CBF genes reside at FROST RESISTANCE-H2, one of two loci having major effects on winter-hardiness. FR-H2 was revealed in a population derived from the winter barley 'Nure' and the spring barley 'Trèmois'. 'Nure' harbors two to three copies of CBF2A and CBF4B as a consequence of tandem iteration of the genomic region encompassing these genes whereas 'Trèmois' harbors single copies, and these copy number differences are associated with their transcript level differences. Here we explore further the relationship between FR-H2 CBF gene copy number and transcript levels using 'Admire', a winter barley accumulating FR-H2 CBF gene transcripts to very high levels, and a group of lines related to 'Admire' through descent. DNA blot hybridization indicated the CBF2A-CBF4B genomic region is present in 7-8 copies in 'Admire' and is highly variable in copy number across the lines related to 'Admire'. At normal growth temperatures transcript levels of CBF12, CBF14, and CBF16 were higher in lines having greater CBF2A-CBF4B genomic region copy numbers than in lines having fewer copy numbers at peak expression level time points controlled by the circadian clock. Chromatin immunoprecipitation indicated CBF2 was at the CBF12 and CBF16 promoters at normal growth temperatures. These data support a scenario in which CBF2A-CBF4B genomic region copy numbers affect expression of other FR-H2 CBFs through a mechansim in which these other FR-H2 CBFs are activated by those in the copy number variable unit.
C-重复结合因子（CBFs）是通过拟南芥鉴定出的DNA结合转录激活因子。在大麦（Hordeum vulgare）中，一组CBF基因位于抗冻性-H2（FROST RESISTANCE-H2）位点，该位点是对冬性有主要影响的两个位点之一。FR-H2是在源自冬大麦“纽尔（Nure）”和春大麦“特雷穆瓦（Trèmois）”的群体中发现的。由于包含这些基因的基因组区域串联重复，“纽尔”含有两到三个CBF2A和CBF4B拷贝，而“特雷穆瓦”含有单拷贝，并且这些拷贝数差异与它们的转录水平差异相关。在这里，我们使用“爱慕（Admire）”（一种积累FR-H2 CBF基因转录本至非常高水平的冬大麦）以及一组通过谱系与“爱慕”相关的品系，进一步探究FR-H2 CBF基因拷贝数与转录水平之间的关系。DNA印迹杂交表明，CBF2A-CBF4B基因组区域在“爱慕”中存在7至8个拷贝，并且在与“爱慕”相关的品系中拷贝数高度可变。在正常生长温度下，在由生物钟控制的峰值表达水平时间点，具有较高CBF2A-CBF4B基因组区域拷贝数的品系中，CBF12、CBF14和CBF16的转录水平高于拷贝数较少的品系。染色质免疫沉淀表明，在正常生长温度下，CBF2位于CBF12和CBF16启动子处。这些数据支持这样一种情况，即CBF2A-CBF4B基因组区域拷贝数通过一种机制影响其他FR-H2 CBF的表达，在这种机制中，其他FR-H2 CBF由拷贝数可变单元中的那些因子激活。
