The subcellular localisation of mRNA transcripts during development can play a key role in the control of patterning and differentiation. In Drosophila embryos, the mRNAs of some developmental genes, such as wingless, are localised by their active transport along microtubules by the dynein complex. Now, on , Henry Krause and co-workers identify a consensus motif for the transport of RNA to the apical cytoplasm of fly embryos. By using an embryo microinjection assay, the researchers identify an element (WLE3) in the 3′UTR of winglessmRNA that is necessary and sufficient for the apical transport of wingless mRNA in preblastoderm Drosophila melanogasterembryos. By examining wingless mRNA sequences in other Drosophila species, the researchers show that WLE3 has a highly conserved stem-loop structure. Mutagenic analysis, however, indicates that only a few key residues, base pairs and bulges in WLE3 are required for its activity. These essential features are also present in other apical localization elements and might, therefore, define the first consensus motif for apical RNA transport.
