Fig. 8. Ectopic expression of Doc together with pnr and tin promotes cardioblast specification. (A-F) Cardioblasts of representative stage 15-16 embryos labeled for mid mRNA and Mef2 protein. All images are projections of confocal scans merged as in Fig. 5. (A) Wild-type embryo showing single-cell bilateral rows of cardioblasts. (B) Ectopic expression of Doc2 throughout the dorsal mesoderm using tinD-GAL4/UAS-Doc2 produces extra cardioblasts (arrowheads). (C) Combined expression of pnr+tin leads to a similar number of supernumerary cardioblasts as with UAS-Doc2. (D) Combined expression of Doc2+tin produces even more cardioblasts than with UAS-Doc2 alone. (E) UAS-Doc2+UAS-pnr and (F) UAS-Doc2+UAS-pnr+UAS-tin driven by tinD-GAL4 produce the strongest increase in cardioblast number, with almost twice as many cardioblasts as in wild type. (G) Lateral view of stage 14 wild-type embryo stained for mid mRNA and Mef2, showing a single row of cardioblasts. (H) Embryo as in G, but with twi-GAL4-driven expression of Doc2, pnr and tin, which shows a dramatic expansion of myocardial mid expression (arrowhead). (I) Stage 16 wild-type embryo stained for the pericardial cell markers Zfh-1, Odd and Eve as in Fig. 4A. (J) tinD-GAL4/UAS-Doc2 embryo stained as in I, showing fewer pericardial cells, especially of the Odd-PC type (yellow). Eve-PCs (pink) and DA1 muscles (blue) are only mildly affected. A reduction of Odd⁺ cells is also seen in the lymph gland. (K) Combined expression of pnr and tin in the dorsal mesoderm leaves the majority of the pericardial cells intact, although some Eve-PCs and Odd-PCs are missing (bracket). (L) Combined overexpression with UAS-Doc2+UAS-pnr+UAS-tin leads to a severe reduction of all types of pericardial cells, although Eve-PCs (pink) are retained more frequently.