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.