Fig 4.

Activity of Xema activator and repressor constructs. (A) VP-Xema-mediated inhibition of mesoderm formation. RT-PCR analysis of animal caps dissected at late blastula stages and cultured until midgastrula stages. 1 ng of VP-Xema RNA was injected at early cleavage stages, as listed. Activin (0.5 ng/ml) was added to stage 9 animal caps, as listed. (B) Expression of EnR-Xema induces mesoderm. RT-PCR analysis of animal caps dissected at late blastula stages and cultured until midgastrula stages. 1 ng of EnR-Xema RNA was injected at early cleavage stages, as listed. (C) Expression of EnR-Xema induces ectopic structures. Whole-mount immunohistochemistry of tailbud stage embryos using the somite-specific antibody 12/101; lateral views, anterior is to right. Embryos were stained with X-Gal as a substrate prior to immunohistochemistry. The embryo on the right was co-injected with 100pg β-Galactosidase and 1ng Xema RNA in the animal pole at the 2-cell stage; note the absence of somite staining (red) in the secondary structure containing the β-galactosidase activity (blue). The embryo on the left was injected with 100pg β-Galactosidase RNA in the animal pole at the 2-cell stage and was not probed with the somite-specific antibody.