Fig. 4. pygo is required for Wg signaling in the embryo. (A-E) Micrographs of cuticles of wild-type (A), wg^CX4 (B), pygo¹⁰ maternal/zygotic mutant (C), a pygo¹⁰ maternal mutant without (D) or with (E) a P[UAS- pygo] transgene. The mothers in D,E are heterozygous for P[Da-Gal4]. The absence of maternal and zygotic pygo results in a denticle lawn similar to that observed in wg mutants (compare panel B with C). Paternal rescue of the pygo germline clone gives a variable phenotype (see Table 1 for more details), with most cuticles having four to seven abdominal denticles (the one in D has six). Further rescue was observed with the P[UAS- pygo] transgene driven by P[Da-Gal4] (Table 1), with the example shown in E having seven denticles (arrow indicates the partial fusion of the fourth and fifth abdominal denticles belts). (F-N) Confocal images of wild type (F,I,L), wg^CX4 (G,J,M) or pygo¹⁰ maternal/zygotic mutant embryos (H,K,N) stained with antibodies against En (F-H), Wg (I-K) or Eve (L-N). The embryos in F-K are at mid-stage 10 and the ones in L-N are at stage 13. Embryos that lack zygotic pygo were unambiguously identified by the absence of eve-lacZ staining. Note that at mid-stage 10 (judged by the extent of stomodeum invagination), when wild-type and wg mutants are at full germband extension (most clear in F and I), the pygo mutants have incomplete extension (clear in H but even more obvious in K). As described in the text, the En and Wg stripes are largely absent at this stage in pygo mutants (H,K), though the residual epidermal En expression (arrows) is not observed in wg mutants (G). The Eve pericardial expression (arrow in L) is absent in wg and pygo mutants (arrows in M and N), while Eve expression in the CNS is present (arrowheads).

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