Figure 7.

Ubx protein levels are modulated in the third leg epithelium, but the levels in apical and preapical bristle precursors are similar. Confocal images of distal tibia and basitarsus of third leg of neu-lacZ flies 2.5 h APF (A,B) and 4.5 h APF (C–F). In green and right-hand panels anti-Ubx staining; in red anti-β-galactosidase staining. (A,B) Third leg 2.5 h APF. In the area reproduced here, Ubx protein levels are modulated: Expression is higher in posterior (P) than anterior leg (A); levels are higher in anterior distal tibia than anterior basitarsus; levels are reduced in anterior distal tibia in a dorsal strip containing sensory organ precursors and in the invaginating cells of the tibial chordotonal organ (see outline marked by asterisk in B). The first-order precursors of apical (arrowhead) and preapical bristle (double arrowhead) show similar levels of Ubx expression (see outlines marked with arrowheads in B). (C,D) Dorsal and (E,F) ventral aspects of distal tibia and basitarsus of a third leg at 4.5 h APF. By this time, the second-order precursors of apical and preapical bristle have formed. Ubx levels in these precursors are still comparable; Ubx levels in the tibial-chordotonal organ remain reduced (see outlines marked with arrowheads respectively asterisk in D and F).