In mammals and plants, parental genomic imprinting, which results from mitotically stable epigenetic modifications, restricts the expression of specific loci to one parental allele. During gametogenesis in mammals, imprinting involves sex-dependent de novo DNA methylation and non-coding RNAs but does a comparable mechanism operate in plants? Here (p. 2953), Thiet Minh Vu, Frédéric Berger and colleagues report that de novo RNA-directed DNA methylation (RdDM), which depends on small interfering RNAs, regulates imprinting at several loci in Arabidopsis endosperm. By dissecting the expression of various members of the RdDM pathway, the researchers show that RdDM is required in somatic tissues to silence both parental alleles, whereas repression of RdDM in female gametes contributes to the activation of the maternal allele. Hence, both de novo DNA methylation and non-coding RNAs play a role in the regulation of imprinted loci in plants and mammals, which suggests that convergent evolutionary processes contribute to imprinting in these distinct groups of eukaryotes.