The regulation of parental genome dosage is of fundamental importance in animals and plants, as exemplified by X-chromosome inactivation and dosage compensation. The 'triploid block' is a classic example of dosage regulation in plants that establishes a reproductive barrier between species differing in chromosome number^1,2. This barrier acts in the embryo-nourishing endosperm tissue and induces the abortion of hybrid seeds through a yet unknown mechanism ³ . Here we show that depletion of paternal epigenetically activated small interfering RNAs (easiRNAs) bypasses the triploid block in response to increased paternal ploidy in Arabidopsis thaliana. Paternal loss of the plant-specific RNA polymerase IV suppressed easiRNA formation and rescued triploid seeds by restoring small-RNA-directed DNA methylation at transposable elements (TEs), correlating with reduced expression of paternally expressed imprinted genes (PEGs). Our data suggest that easiRNAs form a quantitative signal for paternal chromosome number and that their balanced dosage is required for post-fertilization genome stability and seed viability.

中文翻译：

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父本easiRNA调节拟南芥中亲本基因组的剂量。

亲本基因组剂量的调节在动植物中至关重要，例如X染色体失活和剂量补偿。“三倍体阻滞”是植物中剂量调节的经典示例，可在^1,2号染色体不同的物种之间建立生殖屏障。该屏障作用于滋养胚乳的胚乳组织，并通过未知的机制诱导杂种种子的流产³。在这里，我们显示父系表观遗传激活的小干扰RNA（easiRNAs）的耗竭绕开了三倍体阻滞，以响应拟南芥中父本倍性的增加。父本植物特异性RNA聚合酶IV的丢失通过在转座因子（TEs）恢复小RNA定向的DNA甲基化抑制了easiRNA的形成并拯救了三倍体种子，这与父本表达的印迹基因（PEGs）的表达降低有关。我们的数据表明，easiRNA形成了父染色体数目的定量信号，并且受精后基因组稳定性和种子活力需要平衡剂量。