Department of Cell and Developmental Biology, John Innes Centre, Norwich NR4 7UH, UK.
Science. 2021 Jul 2;373(6550). doi: 10.1126/science.abh0556.
The plant male germline undergoes DNA methylation reprogramming, which methylates genes de novo and thereby alters gene expression and regulates meiosis. Here, we reveal the molecular mechanism underlying this reprogramming. We demonstrate that genic methylation in the male germline, from meiocytes to sperm, is established by 24-nucleotide small interfering RNAs (siRNAs) transcribed from transposons with imperfect sequence homology. These siRNAs are synthesized by meiocyte nurse cells (tapetum) through activity of CLSY3, a chromatin remodeler absent in other anther cells. Tapetal siRNAs govern germline methylation throughout the genome, including the inherited methylation patterns in sperm. Tapetum-derived siRNAs also silence germline transposons, safeguarding genome integrity. Our results reveal that tapetal siRNAs are sufficient to reconstitute germline methylation patterns and drive functional methylation reprogramming throughout the male germline.
植物雄性生殖细胞经历 DNA 甲基化重编程，该过程从头甲基化基因，从而改变基因表达并调控减数分裂。在这里，我们揭示了这种重编程的分子机制。我们证明，雄性生殖细胞（从减数分裂细胞到精子）中的基因甲基化是由转座子转录的 24 个核苷酸小干扰 RNA（siRNA）建立的，这些转座子具有不完全序列同源性。这些 siRNA 通过染色质重塑因子 CLSY3 在减数分裂细胞滋养细胞（绒毡层）中合成，CLSY3 在其他花药细胞中不存在。绒毡层 siRNA 调控整个基因组中的生殖细胞甲基化，包括精子中的遗传甲基化模式。绒毡层衍生的 siRNA 还可以沉默生殖细胞转座子，保护基因组完整性。我们的结果表明，绒毡层 siRNA 足以重建生殖细胞甲基化模式，并驱动整个雄性生殖细胞的功能甲基化重编程。
