Fig. 7. Ubx is not required for heart specification, but can partially induce ectopic heart formation. (A) UBX levels (green) are reduced by ectopic expression of abd-A. Inset shows MEF2 accumulation (red) in the same sample at the same focal plane. (B-D) Ubx^9.22 homozygotes stained for MHC accumulation (B), Tina-1 expression (C) and ABDA accumulation (D). Note that there is no effect of loss of Ubx function upon the specification of the heart, despite a slight increase in ABDA levels in the aorta. Arrow in B identifies one of the two ostia formed by S6.

(E.H) Effects of ectopic expression of Ubx upon dorsal vessel cell identity. (E) UBX accumulation is at high levels throughout the mesoderm. (F) MHC accumulation indicates that the heart region is still formed in these embryos, and that additional ostia are occasionally observed in cells which would normally form the aorta (arrow). (G) Tina-1 expression is now detected throughout the dorsal vessel. (H) abd-A expression is normal in these embryos. The normal location of the heart is bracketed in A-D. All panels are dorsal views of stage 16 embryos oriented with anterior towards the left. Scale bar: 50 µm.