BAP-tagged versions of the Tsl and GD proteins are functional.

(A) Wild-type first instar larval cuticle showing ventral denticle bands (vd, arrow) and Filzkörper (Fk, arrowhead) structures. (B) Embryonic cuticle produced by a mother expressing Tsl-BAP throughout the follicle cell layer under the control of the CY2-Gal4 driver element. As seen previously with wild-type Tsl [65, 66, 75], uniform expression in the follicle cell layer leads to the formation of progeny embryos that are made entirely of terminal pattern elements. The segmented regions of the embryo are suppressed, with the loss of ventral denticles and the presence of patches of Filzkörper material (Fk, arrowheads) that have formed in the central region of the embryo. (C) Embryonic cuticle produced by a mother expressing GD-BAP mRNA in ovarian nurse cells under the control of the Nanos-Gal4::VP16 driver element. As has been seen for wild-type GD protein [76], transgenic overexpression in the female germline leads to the formation of ventralized embryos. Pattern elements that are normally found in dorsal and dorsolateral regions of the larvae, such as Filzkörper, are absent, while there is an expansion of ventral structures such as ventral denticles (vd, arrows) around the DV circumference of the embryo.