背景回顾-1：The triploid block, which prevents interploidy hybridizations in flowering plants, is characterized by a failure in endosperm development, arrest in embryogenesis, and seed collapse. 

背景回顾-2：：Many genetic components of triploid seed lethality have been successfully identified in the model plant Arabidopsis thaliana, most notably the paternally expressed genes (PEGs), which are upregulated in tetraploid endosperm with paternal excess. 

前期基础：Previous studies have shown that the paternal epigenome is a key determinant of the triploid block response, as the loss of DNA methylation in diploid pollen suppresses the triploid block almost completely. 

主要发现：Here, we demonstrate that triploid seed collapse is bypassed in Arabidopsis plants treated with the DNA methyltransferase inhibitor 5-Azacytidine during seed germination and early growth. 

结果1：We identified strong suppressor lines showing stable transgenerational inheritance of hypomethylation in the CG context, as well as normalized expression of PEGs in triploid seeds.

结果2：Importantly, differentially methylated loci segregate in the progeny of “epimutagenized” plants, which may allow epialleles involved in the triploid block response to be identified in future studies. 

结果3：Finally, we demonstrate that chemically induced epimutagenesis facilitates hybridization between different Capsella species, thus potentially emerging as a strategy for producing triploids and interspecific hybrids with high agronomic interest.

 摘 要 

三倍体障碍防止了开花植物的多倍体杂交，其特征是胚乳败育、胚胎发生停滞和种子衰败。在模式植物拟南芥中，目前已成功鉴定出许多三倍体种子致死的遗传组分，尤其是在四倍体胚乳中上调表达、且来自于父本转录本贡献更大的父系表达基因（PEG）。先前的研究表明，父系表观基因组是三倍体障碍响应的关键决定因素，因为二倍体花粉中DNA甲基化的缺失能够几乎完全抑制三倍体障碍。本文中，作者发现在拟南芥种子萌发和早期生长过程中，用DNA甲基转移酶抑制剂5-氮杂胞苷处理能够绕过三倍体种子衰败。作者鉴定了在CG序列上表现出稳定的低甲基化跨世代遗传的强抑制株系，以及三倍体种子中PEGs基因的正常表达。重要的是，差异的甲基化位点在“表观诱变”的植物后代中出现分离，这可能有助于在未来的研究中鉴定到参与三倍体障碍响应的表观等位基因。最后，作者揭示了化学诱导的表观诱变促进了不同荠属植物之间的杂交，因此有可能成为将来创制具有高农艺价值的种间杂种和三倍体相关策略制定提供参考。