Grupo de Desarrollo Reproductivo y Apomixis, Laboratorio Nacional de Genómica para la Biodiversidad y Departamento de Ingeniería Genética de Plantas, Cinvestav Irapuato, México.
Plant Signal Behav. 2010 Nov;5(11):1476-9. doi: 10.1038/nature08828. Epub 2010 Nov 1.
Recent evidence indicates that the establishment of the haploid phase of the plant life cycle requires epigenetic mechanisms that control reproductive cell fate. We previously showed that in Arabidopsis thaliana (Arabidopsis) mutations in ARGONAUTE9 (AGO9) result in defective cell specification during megasporogenesis. AGO9 preferentially interacts with 24 nucleotide (nt) small RNAs (sRNAs) derived from transposable elements (TEs), and its sporophytic activity is required to silence TEs in the female gametophyte. Here we show that AGO9 can bind in vitro to 24 nt sRNAs corresponding to Athila retrotransposons expressed in the ovule prior to pollination. We also show that AGO9 is necessary to inactivate a significant proportion of long terminal repeat retrotransposons (LTRs) in the ovule, and that its predominant TE targets are located in the pericentromeric regions of all 5 chromosomes, suggesting a link between the AGO9-dependent sRNA pathway and heterochromatin formation. Our extended results point towards the existence of a tissue-specific mechanism of sRNA-dependent TE silencing in the ovule.
最近的证据表明，植物生命周期的单倍体阶段的建立需要控制生殖细胞命运的表观遗传机制。我们之前曾表明，在拟南芥（Arabidopsis）中，ARGONAUTE9（AGO9）的突变导致在大孢子发生过程中出现有缺陷的细胞特化。AGO9 优先与来自转座元件（TEs）的 24 核苷酸（nt）小 RNA（sRNA）相互作用，其孢子体活性是沉默雌性配子体中 TEs 所必需的。在这里，我们表明 AGO9 可以在体外与在授粉前胚珠中表达的 Athila 反转录转座子相对应的 24nt sRNA 结合。我们还表明，AGO9 对于失活胚珠中相当一部分长末端重复反转录转座子（LTRs）是必需的，并且其主要的 TE 靶标位于所有 5 条染色体的着丝粒区域，这表明 AGO9 依赖的 sRNA 途径与异染色质形成之间存在联系。我们的扩展结果表明，在胚珠中存在一种组织特异性的 sRNA 依赖性 TE 沉默机制。
