Fig. 5. Expression of Ubx, Abd-A, Abd-B in the cardiac tube. Immunostaining with anti-Ubx (A-C; red), anti-Abd-A (D-F; red), anti-Abd-B (G-I; red) or double labeling with anti-Tin (A, green), anti--Spectrin (B,C,E,F,H,I; green) and anti-ß-gal (D,G; green). Open arrowheads indicate svp-expressing cardioblasts in the aorta; solid arrowheads indicate svp-expressing cardioblasts in the heart. (A,D,G) Wild-type embryos. Ubx (in A) is expressed in all the cardioblasts (arrow) in the A2 to A5 segments (yellow) including the svp-expressing cells (red) that do not express Tin and a subset of pericardiac cells (asterisks). Abd-A (in D) is expressed in the cardioblasts (arrow) in the A5 to A7 segments, including the svp-expressing cells (yellow). Abd-B (in G) is expressed in the four posterior most cardioblasts (arrows) and, to a lesser extent, in the svp-expressing cells in segment A7. (B,H) abd-A^m4 mutant embryos. Ubx (in B) is ectopically expressed in cardioblasts in the posterior A5 to A7 segments (arrows), including the svp-expressing cells. Abd-B (in H) expression is as in wild-type embryos (arrows). (C) UAS-abd-A, twist-GAL4 embryos. Ubx expression in the aorta (A1-A5 segments) is considerably less than in wild-type embryos. tin-expressing cardioblasts (arrows) and svp-expressing cardioblasts. (E) Ubx^9.22 mutant embryos. The expression of Abd-A is as in wild-type embryos (arrows). (F) UAS-Ubx, twist-GAL4 embryos. Abd-A expression is as in wild-type embryos (arrows). (I) Ubx, abd-A double mutant embryos. Abd-B expression is as in wild-type embryos (arrows). The large arrow points to the ectodermal cells expressing Abd-B.

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