Fig. 7. Model for hindgut elongation by Upd/JAK/STAT signaling. Expression of upd in the small intestine (SI) under the control of Drm and Lin results in the formation of a gradient of Upd protein in cells posterior to the small intestine. In response to signaling by Upd, a gradient of Stat92E is established; this leads to the orientation of cell rearrangement in the hindgut.