Figure 6.

Model of the functional interactions of Pnr, Tin, and Ush during cardial and pericardial cell specification, based on loss- and gain-of-function phenotypes. The arrow indicates a positive requirement for Tin and Pnr in cardial cell formation, whereas the solid blocked line indicates a negative role for the pnr, ush, and/or tin genetic combination in this process. The hatched blocked line indicates a negative function for these genes in the Eve-expressing pericardial cells. The model is a simplification of the total genetic complexity of cardiac cell specification in Drosophila and does not necessarily list all components required to control the production of these distinct cell types.