Distribution of FoxK in Drosophila embryos. (A and B) Distinct temporal accumulation of the FoxK-L and FoxK-S transcripts by RT-PCR. FoxK-L is present in unfertilized embryos (UE), pupae (P), and head (H) and in thorax (T) and abdomen (Ab) from adult flies (A). FoxK-S accumulates in embryos (E) and salivary glands (SG) and gut from larvae (L). (C and D) In situ hybridization of wild-type embryos using digoxigenin-labeled FoxK-mRNA probes. In stage 16 embryos, the sense probe results in negative signal (C), whereas FoxK mRNA accumulates in the endoderm of parasegments (PS) 3 and 7 (D). (E and F) Single focal plane of whole-mount wild-type embryos stained with anti-FoxK antibody. (E) Stage 15 embryos revealed nuclear FoxK signal in the lining of the single vesicle of the midgut endoderm (arrow). (F) Stage 16 embryos accumulate FoxK in the lining of all four vesicles of the midgut endoderm and gastric constrictions (arrow). (G) Ventral view of an embryo showing FoxK (green) expression along the ventral nerve cord also labeled with anti-Elav (merged image). (H and I) Detail of G showing FoxK and Elav colocalization in the nuclei of ventral cord neurons (H, merge) or FoxK alone (I). All embryos are oriented with the anterior end to the left.