Fig. 8.

Toy and ISWI maintain the fate of the ocellar and head epidermis domains. (A) otd is expressed within the ocellar and dorsal epidermis domains of wild-type eye-antennal discs. (B-E) otd is first lost within the head epidermis region (arrow in B) at 96 h AEL but is subsequently re-activated in cells between the two antennal fields by 108 h (arrow in E). These cells will form new head epidermis tissue. (F,K) wg and dpp are expressed in the dorsal and ventral domains, respectively, of the wild-type antennal disc. (G-J) During development of the second antenna, wg expression begins to be activated starting at 96 h AEL (arrow in G). (L-O) Expression of dpp follows and is activated in regions that will give rise to the second antenna at 100 h AEL (arrow in M). The juxtaposition of the wg and dpp domains triggers the formation of the second antenna as it does in the endogenous antenna. Scale bar: 50 µm.