单细胞 RNA 测序揭示 MBD5、MBD6 和 SILENZIO 在发育中的花粉营养细胞中维持沉默。
Single-nucleus RNA-seq reveals that MBD5, MBD6, and SILENZIO maintain silencing in the vegetative cell of developing pollen.
机构信息
Molecular Biology Institute, University of California Los Angeles, Los Angeles, CA 90095, USA; Department of Molecular, Cell and Developmental Biology, University of California Los Angeles, Los Angeles, CA 90095, USA.
Department of Molecular, Cell and Developmental Biology, University of California Los Angeles, Los Angeles, CA 90095, USA.
出版信息
Cell Rep. 2022 Nov 22;41(8):111699. doi: 10.1016/j.celrep.2022.111699.
Silencing of transposable elements (TEs) drives the evolution of numerous redundant mechanisms of transcriptional regulation. Arabidopsis MBD5, MBD6, and SILENZIO act as TE repressors downstream of DNA methylation. Here, we show, via single-nucleus RNA-seq of developing male gametophytes, that these repressors are critical for TE silencing in the pollen vegetative cell, a companion cell important for fertilization that undergoes chromatin decompaction. Instead, other silencing mutants (met1, ddm1, mom1, morc) show loss of silencing in all pollen nucleus types and somatic cells. We show that TEs repressed by MBD5/6 gain chromatin accessibility in wild-type vegetative nuclei despite remaining silent, suggesting that loss of DNA compaction makes them sensitive to loss of MBD5/6. Consistently, crossing mbd5/6 to histone 1 mutants, which have decondensed chromatin in leaves, reveals derepression of MBD5/6-dependent TEs in leaves. MBD5/6 and SILENZIO thus act as a silencing system particularly important when chromatin compaction is compromised.
转座元件 (TEs) 的沉默驱动了许多冗余转录调控机制的进化。拟南芥 MBD5、MBD6 和 SILENZIO 作为 DNA 甲基化下游的 TE 抑制剂发挥作用。在这里，我们通过发育中的雄性配子体的单核 RNA-seq 显示，这些抑制剂对于花粉营养细胞中的 TE 沉默至关重要，花粉营养细胞是一个对于受精很重要的伴随细胞，经历染色质解压缩。相比之下，其他沉默突变体（met1、ddm1、mom1、morc）在所有花粉核类型和体细胞中都显示出沉默的丧失。我们表明，尽管 MBD5/6 抑制的 TEs 在野生型营养核中保持沉默，但它们获得了染色质可及性，这表明 DNA 压缩的丧失使它们对 MBD5/6 的丧失敏感。一致地，将 mbd5/6 与组蛋白 1 突变体杂交，该突变体在叶片中具有去凝聚的染色质，揭示了 MBD5/6 依赖性 TEs 在叶片中的去抑制。因此，MBD5/6 和 SILENZIO 作为一种沉默系统，在染色质压缩受到损害时尤为重要。
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