Non-cell autonomous small RNA silencing in female gametes and early embryo of Arabidopsis. Non-cell autonomous small RNA silencing in female gametes and early embryo of Arabidopsis

In recent years, small RNA movement has been both hypothesized and shown to be an integral part of the epigenetic DNA methylation reprogramming occurring during plant reproduction. It was suggested that the release of epigenetic silencing in accessory cell types or tissues is necessary to reinforce epigenetic silencing in the gametes (egg cell and sperm cells) which would in turn ensure the genomic stability of the next generation plant. Small RNA movement was indeed shown to occur during male gametogenesis. However, the situation within the female gametophyte and in early seed development is mostly unknown. Here, we show that small RNA can induce non-cell autonomous silencing from the central cell towards the egg cell but also from the synergids to the egg cell and central cell. In addition, we also observe a non-cell-autonomous silencing from the central cell and/or endosperm towards the early embryo. Our data shows, that in addition to the movement of sRNAs during pollen development, sRNAs movement also occurs in the female gametes.

近年来，小分子RNA（small RNA）的移动不仅被学界提出假说，更已被证实是植物生殖过程中发生的表观基因组DNA甲基化重编程的核心组成部分。此前有研究提出，辅助细胞类群或组织中的表观遗传沉默解除，对于强化配子（卵细胞与精子细胞）内的表观遗传沉默必不可少，而这一过程可进而保障下一代植物的基因组稳定性。已有研究证实，小分子RNA移动确实发生在雄配子发生阶段。然而，雌配子体及种子早期发育中的相关情况，目前仍大多未知。本研究证实，小分子RNA可介导从中央细胞向卵细胞的非细胞自主性沉默，同时也可实现助细胞向卵细胞与中央细胞的非细胞自主性沉默。此外，本研究还观察到从中央细胞和/或胚乳向早期胚胎的非细胞自主性沉默现象。本研究数据表明，除花粉发育阶段的小分子RNA移动外，雌配子中同样存在小分子RNA的移动过程。