| |
Fig. 4. Delayed activation of Siamois leads to repression of ventral gene expression. Embryos were injected ventrally with 50 pg/bl GR-Sia mRNA and 400 pg/bl LacZ mRNA at the four-cell stage and DEX (10 μM) was either omitted (−DEX), or added 15 min before stage 9 (9−), or at stage 9.5. β-Galactosidase activity was revealed in red, and embryos were then processed for in situ hybridisation. In all panels, dorsal is up. Note that the ventral genes PV.1 and Xwnt8 were repressed by GR-Sia activated at stage 9− or at stage 9.5. However, PV.1 expression was repressed several cell diameters away from the injected cells upon early DEX treatment (bracket), whereas it was found adjacent to the injected cells upon late DEX treatment. |
