Fig. 6. pannier promotes the development of all heart cells. Lateral views of stage 15 (A-F) and stage 11 (G-I) embryos as well as high-magnification dorsal views of stage 16 (J-L) embryos of the indicated genotypes labeled for the indicated proteins. (A) Wild-type embryo showing two bilateral rows of cardioblasts (arrow). (B) In pnr¹ embryos, most cardioblasts do not develop, although short stretches of cardioblasts still arise in this background (arrow). (C) In pnr^VX6 embryos, cardioblasts almost never develop (arrow indicates normal position of the cardioblast row). (D) Wild-type embryo showing one of the two bilateral rows of pericardial cells (arrow). (E) In pnr¹ embryos, there is a strong decrease in pericardial cells (arrow). (F) pnr^VX6 embryos exhibit a more severe loss of pericardial cells (arrow). (G) In wild-type embryos Tin expression marks the cardiac mesoderm (arrowheads) and the presumptive visceral mesoderm (arrows). In (H) pnr¹ and (I) pnr^VX6 embryos, Tin expression is almost completely absent from the cardiac mesoderm (arrowheads) but is essentially wild type in the visceral mesoderm. (J) Wild-type embryo labeled for Mef2 (green) and Svp-lacZ (red) showing the normal reiterative pattern of four Svp-lacZ negative cardioblasts and two Svp-lacZ positive cardioblasts per hemisegment. (K) pnr¹ embryos retain the 2:1 ratio of Svp-lacZ-negative to Svp-lacZ-positive cardioblasts although the precise alignment of these cardioblasts is perturbed (arrowheads indicate cardioblasts). (L) pnr¹ pnt⁰¹²³⁰⁹ embryos exhibit localized overproduction of cardioblasts (arrowheads) and the majority of these cardioblasts express Svp-lacZ (yellow or orange cells). Broken white lines in K and L separate images taken from two different embryos of the indicated genotype. Anterior is towards the left.