Figure 10. Expression of key genes affect scale fate decisions and influence downstream pigmentation state.

During early-instar development, wing disc cells differentiate into presumptive scale cells (PSCs). Throughout fifth-instar growth, PSCs express key scale cell specification genes such as cortex, which induce differentiation into Type II (optix−) scales or Type III (optix+) scales. In the absence of cortex, scale cells differentiate into Type I scales, which differ in pigmentation state based on 3-OHK synthesis controlled by aristaless1 expression. Model based on the epigenetic landscape (Waddington) and by observations made by Gilbert et al., 1987.