Plant Epigenetics Unit, Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna-son, Okinawa 904-0412, Japan.
Sci Rep. 2017 Mar 24;7:45166. doi: 10.1038/srep45166.
Defense mechanisms of plant genomes can epigenetically inactivate repetitive sequences and exogenous transgenes. Loss of mutant phenotypes in intronic T-DNA insertion lines by interaction with another T-DNA locus, termed T-DNA suppression, has been observed in Arabidopsis thaliana, although the molecular basis of establishment and maintenance of T-DNA suppression is poorly understood. Here we show that maintenance of T-DNA suppression requires heterochromatinisation of T-DNA sequences and the nuclear proteins, INCREASED IN BONSAI METHYLATION 2 (IBM2) and ENHANCED DOWNY MILDEW 2 (EDM2), which prevent ectopic 3' end processing of mRNA in atypically long introns containing T-DNA sequences. Initiation of T-DNA suppression is mediated by the canonical RdDM pathway after hybridisation of two T-DNA strains, accompanied by DNA hypermethylation of T-DNA sequences in the F1 generation. Our results reveal the presence of a genome surveillance mechanism through genome hybridisation that masks repetitive DNAs intruding into transcription units.
植物基因组的防御机制可以通过表观遗传方式使重复序列和外源转基因失活。在拟南芥中，已经观察到内含子 T-DNA 插入系通过与另一个 T-DNA 座相互作用而丧失突变表型，称为 T-DNA 抑制，尽管建立和维持 T-DNA 抑制的分子基础知之甚少。在这里，我们表明 T-DNA 抑制的维持需要 T-DNA 序列的异染色质化和核蛋白 INCREASED IN BONSAI METHYLATION 2 (IBM2) 和 ENHANCED DOWNY MILDEW 2 (EDM2)，它们防止含有 T-DNA 序列的非典型长内含子中外源 3' 端加工 mRNA。T-DNA 抑制的起始是通过两种 T-DNA 菌株杂交后，经典 RdDM 途径介导的，伴随着 F1 代 T-DNA 序列的 DNA 超甲基化。我们的结果揭示了存在一种通过基因组杂交来掩盖侵入转录单位的重复 DNA 的基因组监测机制。
