Fig. 3. Expression of the pair rule gene runt and the homeotic gene labial at embryonic stages 9, 10 and 11. Semi-schematic presentation of the Runt and Labial protein (Lab) patterns in brain NBs (A,C,E) and outer procephalic ectoderm in relation to the en pattern (B,D,F) at stage 9 (st9, A,B), stage 10 (st10, C,F) and stage 11 (st11, E,F) as indicated; numbers (1-3) in B,D,F reflect the temporal sequence of the ectodermal runt domains. Lab expression covers the complete intercalary neuroectoderm and emerging NBs. (E) Note that all trito- and two deutocerebral NBs express Lab; red lines demarcate neuromeric boundaries. (G,H) en-lacZ/Lab double stained head flat preparation. (G) Lab expression covers the en intercalary stripe (is) and partially the en antennal stripe (as; compare with F); broken line marks the anterior boundary of the Lab domain. (H) Higher magnification of the region indicated by black frame (in G) focusing at the level of NBs. Note that the Lab-positive Dv4 is at the same anteroposterior level as the En-positive Dv8. (I,J) en-lacZ/Runt double labelled head flat preparation. (I) In the periphery, Runt expression is confined to the ocular (1) and intercalary (3) ectodermal domain. (J) Higher magnification of region marked by black frame in I, focusing at the level of NBs. Positively stained NBs in H,J are indicated by white labels, negative ones are indicated by black labels; insets in G,I show a lateral view of stage 11 wholemounts; dashed line marks the ventral midline. Anterior (a) is towards the top; dorsal (d) is towards the left. AN, IC, MD, MX, antennal, intercalary, mandibular and maxillary segment, respectively; CL, clypeolabrum; FG, foregut; ML, ventral midline; as, en antennal stripe; hs, en head spot; is, en intercalary stripe.

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