Bottley Andrew, Chapman Natalie H, Koebner Robert M D
Department of Pharmacy, University Nottingham, NG7 2RD, UK.
BMC Genet. 2008 Oct 17;9:65. doi: 10.1186/1471-2156-9-65.
In contrast to diploids, most polyploid plant species, which include the hexaploid bread wheat, possess an additional layer of epigenetic complexity. Several studies have demonstrated that polyploids are affected by homoeologous gene silencing, a process in which sub-genomic genomic copies are selectively transcriptionally inactivated. This form of silencing can be tissue specific and may be linked to developmental or stress responses.
Evidence was sought as to whether the frequency of homoeologous silencing in in vitro cultured wheat callus differ from that in differentiated organs, given that disorganized cells are associated with a globally lower level of DNA methylation. Using a reverse transcription PCR (RT-PCR) single strand conformation polymorphism (SSCP) platform to detect the pattern of expression of 20 homoeologous sets of single-copy genes known to be affected by this form of silencing in the root and/or leaf, we observed no silencing in any of the wheat callus tissue tested.
Our results suggest that much of the homoeologous silencing observed in differentiated tissues is probably under epigenetic control, rather than being linked to genomic instability arising from allopolyploidization. This study reinforces the notion of plasticity in the wheat epi-genome.
与二倍体不同，大多数多倍体植物物种，包括六倍体面包小麦，具有额外一层表观遗传复杂性。多项研究表明，多倍体受同源基因沉默影响，在这个过程中，亚基因组拷贝被选择性地转录失活。这种沉默形式可能具有组织特异性，并且可能与发育或应激反应有关。
鉴于无序细胞与整体较低水平的DNA甲基化相关，研究人员探究了体外培养的小麦愈伤组织中同源沉默的频率是否与分化器官中的不同。使用逆转录PCR（RT-PCR）单链构象多态性（SSCP）平台来检测已知受这种沉默形式影响的20组同源单拷贝基因在根和/或叶中的表达模式，我们在测试的任何小麦愈伤组织中均未观察到沉默现象。
我们的结果表明，在分化组织中观察到的许多同源沉默可能受表观遗传控制，而不是与异源多倍体化引起的基因组不稳定性有关。这项研究强化了小麦表观基因组可塑性的概念。
