Fig. 8

Fig. 8 zbmp2b is ectopically expressed in pregastrula boz mutants. Analysis of zbmp2b expression in wild-type and homozygous boz^m168 mutant embryos prior to the onset of gastrulation. All embryos are oriented with animal pole toward the top and dorsal to the right. (a) In wild-type embryos prior to the onset of gastrulation at 40% epiboly stage, zbmp2b transcripts are not detectable on the dorsal side of the embryo. The region free of zbmp2b message is complementary to the dorsal blastoderm region that expresses nieuwkoid/dharma, shown for reference in a slightly younger wild-type embryo (c). (b) In contrast, zbmp2b transcripts do not clear completely from the dorsal margin in homozygous boz^m168 mutant embryos and the persistent zbmp2b expression is also detected in the dorsal YSL. (d and e) Misexpression of nieuwkoid/dharma RNA is sufficient for the down regulation of zbmp2b expression in wild-type pregastrula embryos. (d) Embryo injected with nieuwkoid/dharma RNA in both blastomeres at the two-cell stage and assayed for zbmp2b expression at 40% epiboly stage. zbmp2b expression is strongly reduced throughout the entire blastoderm. (e) zbmp2b expression at 40% epiboly in wild-type embryo injected with nieuwkoid/dharma RNA in two distant blastomeres at the eight-cell stage. Ectopic and expanded regions of zbmp2b repression are observed (arrows).