Department of Plant Biology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
Linnean Center for Plant Biology, Uppsala, Sweden.
Nat Genet. 2018 Feb;50(2):193-198. doi: 10.1038/s41588-017-0033-4. Epub 2018 Jan 15.
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. This barrier acts in the embryo-nourishing endosperm tissue and induces the abortion of hybrid seeds through a yet unknown mechanism . 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.
亲本基因组剂量的调控在动植物中具有重要意义，例如 X 染色体失活和剂量补偿。“三倍体阻断”是植物中剂量调控的经典例子，它在染色体数不同的物种之间建立了生殖障碍。该障碍作用于胚胎营养的胚乳组织，并通过未知的机制导致杂种种子的流产。在这里，我们表明，在拟南芥中，增加父本的倍性会导致父本表观激活的小干扰 RNA（easiRNA）耗竭，从而绕过三倍体阻断。植物特异性 RNA 聚合酶 IV 的父本缺失抑制了 easiRNA 的形成，并通过恢复转座元件（TEs）的小 RNA 指导的 DNA 甲基化来拯救三倍体种子，这与父本表达的印迹基因（PEGs）的表达降低相关。我们的数据表明，easiRNA 形成了父本染色体数的定量信号，其平衡剂量对于受精后基因组稳定性和种子活力是必需的。
