Chromatin modification contributes to the expression divergence of three TaGS2 homoeologs in hexaploid wheat.
Chromatin modification contributes to the expression divergence of three TaGS2 homoeologs in hexaploid wheat.
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染色质修饰导致六倍体小麦中三个 TaGS2 同源物的表达差异
DOI：
10.1038/srep44677
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发表时间：
2017-03-16
影响因子：
4.6
通讯作者：
Li J
中科院分区：
文献类型：
--
作者：
Zhang W;Fan X;Gao Y;Liu L;Sun L;Su Q;Han J;Zhang N;Cui F;Ji J;Tong Y;Li J
塑料谷氨酰胺合成酶（GS 2）负责铵同化。六倍体小麦中TaGS 2同源基因在育种过程中经历不同选择压力的原因尚不清楚。TaGS2在根中的表达量最低，但在叶中的表达量最高，TaGS2-B的表达量高于TaGS2-A和TaGS2-D。ChIP分析显示，TaGS 2-B在叶片中的表达的激活与增加的H3 K4三甲基化相关。TaGS2在根中的转录沉默与更大的胞嘧啶甲基化和更少的H3K4三甲基化相关。微球菌核酸酶和DNase I可及性实验表明，启动子区在根中比在叶中更耐消化，这表明启动子区的封闭核小体构象对TaGS 2时空表达的转录起始起重要作用。与此相反，转录区域具有不同的核酸酶accessories的三个TaGS 2同源物在同一组织中，这表明转录区域的核小体构象的TaGS 2同源物的微调的一部分。这项研究提供的证据表明，组蛋白修饰，DNA甲基化和核酸酶的可及性协调控制的TaGS 2同源物的转录。我们的研究结果为TaGS 2-B在育种过程中经历最强的选择压力提供了重要证据。
Plastic glutamine synthetase (GS2) is responsible for ammonium assimilation. The reason that TaGS2 homoeologs in hexaploid wheat experience different selection pressures in the breeding process remains unclear. TaGS2 were minimally expressed in roots but predominantly expressed in leaves, and TaGS2-B had higher expression than TaGS2-A and TaGS2-D. ChIP assays revealed that the activation of TaGS2-B expression in leaves was correlated with increased H3K4 trimethylation. The transcriptional silencing of TaGS2 in roots was correlated with greater cytosine methylation and less H3K4 trimethylation. Micrococcal nuclease and DNase I accessibility experiments indicated that the promoter region was more resistant to digestion in roots than leaves, which indicated that the closed nucleosome conformation of the promoter region was important to the transcription initiation for the spatial-temporal expression of TaGS2. In contrast, the transcribed regions possess different nuclease accessibilities of three TaGS2 homoeologs in the same tissue, suggesting that nucleosome conformation of the transcribed region was part of the fine adjustment of TaGS2 homoeologs. This study provides evidence that histone modification, DNA methylation and nuclease accessibility coordinated the control of the transcription of TaGS2 homoeologs. Our results provided important evidence that TaGS2-B experienced the strongest selection pressures during the breeding process.