In many plant species, multiple MIR loci produce identical or functionally equivalent microRNA molecules, but the significance of this genetic redundancy has not been investigated in detail. An example of this is the well-characterized MIR165/6 gene family in Arabidopsis thaliana, where five of the nine MIR165/6 genes exhibit highly homologous expression patterns and act to restrict the expression of HD-ZIP III genes, including PHABULOSA (PHB), within roots, leaves and embryos. In this issue, Hashimoto et al. (on pp. 1017–1026) report that two less well-characterized members of the MIR165/6 gene family are highly expressed in developing ovules and play a major role in restricting PHB expression to promote the outer integuments (primordial seed coat) to surround the embryo sac. This study therefore provides a clue for understanding the significance of having multiple MIR loci in plant development.