Fig. 7.

Mesodermal overexpression of Tup reveals different functional relationships with other cardiac transcription factors. (A-D) Overexpression of Tup leads to a moderate expansion of Tin and some ectopic Tin-expressing cells on the lateral side of the embryo (arrows in B). Overexpression the Pnr allele pnr^D4 results in a strong ectopic induction of Tin across the whole lateral side of the embryo (arrows in C). Co-overexpression of Tup and Pnr^D4 mimics the phenotype of Pnr^D4 overexpression alone (arrows in D point to ectopic Tin-expressing cells). (C1-C3) The ectopic Tin-positive cell clusters induced by overexpression of Pnr^D4 alone are heterogenous. Some cells co-express Tin and Tup (arrow in C3), whereas others are only positive for Tup (arrowhead in C3). (E-I) Tup and Pnr counteract each other in Eve-positive pericardial cell specification. Overexpression of Tup results in additional Eve-positive cells within the clusters (arrows in F), whereas overexpression of Pnr^D4 leads to the complete loss of Eve-positive cell clusters (arrows in G). (H) Co-overexpression of Tup and Pnr^D4 can reduce the effects induced by each factor singly. (I) Pie charts showing the percentage of embryos with wild-type (WT, brown), expanded (+, yellow) or reduced (-, green) Eve-positive cell clusters. (J-M) Overexpression of Tup results in a moderate loss of Odd-positive pericardial cells (arrow in K) and to a strong reduction of Odd-positive lymph gland cells (arrowheads in J,K). Overexpression of Tin has a slightly stronger negative effect on the Odd-positive pericardial cells (arrows in L); however, the reduction of Odd-positive cells in the lymph glands appears to be less strong (arrow in L) than that caused by Tup overexpression (arrowhead in K). (M) Co-overexpression of Tup and Tin results in a similar phenotype to that seen for overexpression of Tin alone. Arrows point to the absence of Odd-positive pericardial cells; the arrowhead points to Odd-positive lymph gland cells.