Fig. 3. B and B act on the Activin/Nodal signalling pathway in Xenopus. (A-C) One-cell embryos were injected with the indicated mRNAs (B, B or EGFP-Smad2) and morpholinos (MoC, MoB or MoB). (A) Overexpression of B, but not B, inhibits elongation of animal caps in response to Activin. (B) Knockdown of B inhibits Activin-induced animal cap elongation, while knockdown of B promotes it. (C) EGFP-Smad2 expression rescues the effect of knocking down B on Activin-induced animal cap elongation. When control embryos had reached stage 8, the animal pole was excised and incubated with or without Activin for 16 hours, and visualised for the degree of elongation.