Fig. 2.

Inductive signals, target genes, and genetic interactions involved in eggshell patterning. (A) The dorsoventral pattern of EGFR signaling. (B) The anteroposterior pattern of DPP signaling. (C) The fate map for the formation of the respiratory dorsal appendages and the operculum. Each of the appendages is derived from a primordium comprising a 2D domain of cells expressing Broad (BR, blue) and an adjacent line of cells expressing Rhomboid (RHO, red). Cells between the two primordia express the transcription factor Pointed (PNT, orange) and contribute to the formation of the operculum. (D) The network of some of the key interactions involved in eggshell patterning. GRK controls br at two different time points: first, when it is distributed in a posterior-to-anterior gradient (P), and then when it is distributed in a dorsoventral (D) gradient (see text for details).