Figure 3.

rho, vn, S and aos are differentially expressed and required in distinct regions of the brain. Stage 9 (st9); red solid line demarcates the wild-typic MAPK domain, according to (a). (a,b) rho is expressed within MAPK domain in DC/PC (solid green line), and in the mesectoderm (‘midline cells’) ventral to TC/DC which are characterized by expression of Single-minded (shown in figure 5n,q). (c) S is broadly expressed in the brain NE, while expression levels vary. (d) vn is expressed in ventral PC and ventral/intermediate DC (solid yellow line), and mesectodermal cells. (e) Scheme summarizes expression data in (a–d), and the EGFR-independent expression of aos in dorsal TC (see also figure 4g and the main text for further explanations). (f) MAPK is strongly reduced in rho^PΔ5 mutant brain NE (red hatched line), when compared with wild-type (a); black arrow indicates faint MAPK in the mutant DC. (g) In vn^RG436 mutants, MAPK is reduced particularly in the ventral PC, and ventral/intermediate DC (red hatched line). For orientation, other abbreviations and symbols see figure 1.