Bread wheat (Triticum aestivum L.) is an allohexaploid grass species (AABBDD genome, 2n = 6x = 42) that arose through hybridization of three related diploid grasses. However, the regulation mechanisms that control the expression of homoeologous genes are poorly understood.

Recently, researchers from Li Junming’s group at the Institute of Genetics and Developmental Biology of Chinese Academy of Sciences reported the underlying mechanism of the expression divergence of three TaGS2 homoeologs in hexaploid wheat.

In their study, the researchers found that 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 demonstrated 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. Their results provided important evidence that TaGS2-B experienced the strongest selection pressures during the breeding process.

Their scientific paper, entitled “Chromatin modification contributes to the expression divergence of three TaGS2 homoeologs in hexaploid wheat”, was published in Scientific Reports (doi: 10.1038/srep44677).

This research was supported by the National Natural Science Foundation of China, the National Key Research and Development Program of China.

Contact:

Li Junming

Center for Agricultural Resources Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences

Email: ljm@sjziam.ac.cn