WINGLESS REPRESSION OF DROSOPHILA FRIZZLED 2 EXPRESSION SHAPES THE WINGLESS MORPHOGEN GRADIENT IN THE WING

In Drosophila wing imaginal discs, the Wingless (Wg) protein acts as a morphogen, emanating from the dorsal/ventral (D/V) boundary of the di sc to directly define cell identities along the D/V axis at short and long range. Here, we show that high levels of a Wg receptor, Drosophil a frizzled 2 (Dfz2), stabilize Wg, allowing it to reach cells far from its site of synthesis. Wg signaling represses Dfz2 expression, creati ng a gradient of decreasing Wg stability moving toward the D/V boundar y. This repression of Dfz2 is crucial for the normal shape of Wg morph ogen gradient as well as the response of cells to the Wg signal. In co ntrast to other ligand-receptor relationships where the receptor limit s diffusion of the ligand, Dfz2 broadens the range of Wg action by pro tecting it from degradation.