Fig. 6

Fig. 6 Regulation of graded bmp ligand transcription by Dharma, FGF and BMP signalling and consequences for the transcriptional activity of the BMP pathway. (A) bmp2b ISH in 30% epiboly wild-type embryos treated with DMSO, LDN-193189 (LDN) or SU5402. (B) bmp2b ISH in 30% epiboly wild-type embryos injected with either control, dharma, or chordin MOs. Ectopic bmp2b expression is detected at the margin upon Dharma knockdown but not in the dorsal ectoderm (white dotted lines). (C) mRFP ISH in BRE-mRFP embryos injected with either control, dharma, or chordin MOs. The fluorescent substrate used in (C) was Fast Blue (pseudocoloured in red). Note that the images are projection of a 10–12 picture stack taken at the margin of the blastoderm to avoid fluorescence from the yolk. (D) Graphical representation of the levels of mRFP, chordin, and bmp2b mRNAs, as well as BMP and p-Smad1/5 proteins across the D/V axis at 30% and 40% epiboly. Between these two stages, Chordin acts to antagonise residual BMP activity dorsally, resulting in a gradient of mRFP at 40% epiboly that reflects the gradient of BMP ligand transcription. For all panels in ((A)–(C)), stages and/or views are indicated. Arrows indicate the limit of the expression domain of the transcripts analysed. V, ventral; D, dorsal.