Zygotic FoxK activity is necessary for midgut differentiation. Midgut development in wild-type (A, D, and G), FoxK⁴⁴ (B, E, and H), and FoxK¹⁶ (C, F, and I) embryos. In FoxK⁴⁴ and FoxK¹⁶ homozygous embryos, the single vesicle of the midgut develops normally until stage 15 (A–C, dashed lines). During stages 16 and 17, wild-type embryos develop four vesicles after the formation of the midgut constrictions (D and G, arrowheads). However, FoxK⁴⁴ homozygous embryos only develop one midgut constriction (E and H, arrowheads), whereas FoxK¹⁶ embryos never develop midgut constrictions (F and I). (J–O) Maternal FoxK is critical for early embryonic development. Differential interference contrast (J–L) and confocal images showing Engrailed (En) expression (M–O) of a normal embryo (J and M) and two different embryos expressing FoxKi under a maternally expressed Gal4-VP16 fusion (tub-Gal4-VP16/UAS-Foxki). The segmental Engrailed stripes are fused (N, arrowhead), split (N and O, arrows), and generally disorganized along the anteroposterior axis.