Engrailed and hedgehog make the range of wingless asymmetric in Drosophilaembryos

In many instances, remote signaling involves the transport of secreted mole cules. Here, we examine the spread of Wingless within the embryonic epiderm is of Drosophila. Using two assays for Wingless activity (specification of naked cuticle and repression of rhomboid transcription), we found that Wing less acts at a different range in the anterior and posterior directions. We show that this asymmetry follows in part from differential distribution of the Wingless protein. Transport or stability is reduced within engrailed-e xpressing cells, and farther posteriorward Wingless movement is blocked at the presumptive segment boundary and perhaps beyond. We demonstrate the rol e of hedgehog in the formation of this barrier.