Fig. 5. Siamois induces expression of Chordin in a direct manner that does not require Smicl. (A) RNA encoding Siamois (500 pg) was injected into embryos of Xenopus laevis at the one-cell stage and animal pole regions were dissected at mid blastula stage 8 (before the mid blastula transition). The animal pole regions were cultured for 3 hours in the presence or absence of cycloheximide, and expression of Chordin was assayed by quantitative RT-PCR. Induction of Chordin is not inhibited by cycloheximide. (B) Expression of Siamois is not inhibited by antisense morpholino oligonucleotides directed against Smicl. Morpholino oligonucleotide XlMO (80 ng) was injected into Xenopus laevis embryos at the one cell stage and expression of Siamois was analysed by quantitative RT-PCR at the indicated stages. (C) RNA encoding Siamois (500 pg) was injected into Xenopus embryos at the one-cell stage either alone or in the presence of the indicated morpholino oligonucleotides. Animal caps were dissected at mid blastula stage 8 and they were cultured to the equivalent of stage 10.5 before being analysed for Chordin expression by quantitative RT-PCR.