Fig. 2. The amnioserosa is not properly patterned in sog^P129D embryos derived from Mad^ES1/+ females. (A) A darkfield photomicrograph of a cuticle of a sog^P129D embryo (lateral view, dorsal up, anterior left). The ventral-most ectodermal cells form the neurogenic ectoderm and are characterized by a segmentally repeated pattern of denticle bands. Dorsolateral cells differentiate dorsal hairs, only faintly visible in the cuticle preparation. The filzkörper, respiratory structures of the tail, are derived from cells in a dorsolateral position in the blastoderm. The amnioserosa, which does not contribute to the embryonic cuticle, can be visualized in a dorsal view of a sog^P129D stage 13 embryo (B) after staining for ß-galactosidase activity from a P[Kr-lacZ] construct expressed in this tissue. (C) Lateral view of a cuticle from a sog^P129D embryo derived from a Mad^ES1/+ female. The internalized filzkörper and the lack of head elements are indicative of a weakly ventralized embryo. The internalization of the filzkörper results from defects in germband extension in embryos that lack a fully functional amnioserosa. The embryo was raised at 25°C. (D) ß-galactosidase activity from the P[Kr-lacZ] construct in a stage 13 sog^P129D embryo derived from a Mad^ES1/+ female. This embryo shows a large reduction in the amount of amnioserosa. Embryos in B and D were raised at 29°C.

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