Late in Drosophila oogenesis, a flat epithelium consisting of somatically derived follicle cells is remodelled into two tubes that secrete proteins that form the long tubular dorsal appendages (DAs), the specialised respiratory structures of the eggshell. On p. 6273, Tran and Berg describe how bullwinkle (bwk), a germline-expressed transcription factor, and shark, a newly identified enhancer of bwk expressed in somatic squamous stretch cells, regulate DA morphogenesis. shark, which encodes a non-receptor tyrosine kinase,was identified as an enhancer of bwk in a genetic-modifier screen. The researchers then used loss- and gain-of-function strategies to show that shark expression in the stretch cells requires bwk activity and that shark is required in the follicle cells for migration of the DA cells. The researchers conclude that shark plays an important downstream role in the bwk-signalling pathway and suggest that this pathway may be conserved in vertebrates.

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