Research Article

Small Silencing RNAs in Plants Are Mobile and Direct Epigenetic Modification in Recipient Cells

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Science  22 Apr 2010:
DOI: 10.1126/science.1187959


A silencing signal in plants with an RNA specificity determinant moves through plasmodesmata and the phloem. To identify the mobile RNA, we grafted Arabidopsis thaliana shoots to roots that would be a recipient for the silencing signal. Using mutants that block small RNA (sRNA) biogenesis in either source or recipient tissue, we demonstrate that transgene-derived and a substantial proportion of the endogenous sRNA had moved across the graft union and we provide evidence that 24nt mobile sRNAs direct epigenetic modifications in the genome of the recipient cells. Mobile sRNA thus represents a mechanism for transmitting the specification of epigenetic modification and could affect genome defense and responses to external stimuli that have persistent effects in plants.