Figure 5.

Pale vs. yellow cell fate decisions in R7 and instruction of R8 (Mikeladze-Dvali et al., 2005). Expression of the transcription factor Spineless in a subset of R7 cells induces yellow fate and Rh4 expression (right). The other R7s express Rh3 by default (left) and send a signal to the underlying R8, which appears to be received by Melted and leads to Rh5 expression. In yellow R8s, the signal is absent and Warts represses Melted as well as Rh5, promoting the default Rh6 fate. Grey indicates repressed genes and inactive regulatory pathways.