Fig. 2. upd and JAK/STAT pathway components are expressed at the anterior of the elongating hindgut. The components of the Drosophila JAK/STAT signaling pathway (ligand Upd, receptor Dome, JAK Hopscotch and STAT) are shown in A and discussed in text. Beginning at stage 9, upd expression is detected in a narrow ring of cells at the anterior of the developing hindgut (at junction with posterior midgut) (B), while expression of dome and Stat92E in this domain is weaker and more diffuse (E,H). By stage 11, expression of upd in the prospective small intestine is strong (C), and increased expression of dome and Stat92E is observed in domains overlapping with, but more extensive than that of upd (F,I, respectively). These expression patterns for upd, dome and Stat92E are maintained throughout embryogenesis (D,GJ, respectively; stage 14). Expression in the anterior hindgut, detected by in situ hybridization, is indicated by brackets (B,C,E,F,H,I) and arrowheads (D,G,J).