Endoderm requires reception of Bmp signaling for proper development. (A-G) Whole-mount images (ventral view) of 5dpf viscerocranium. Asterisks label the ceratobranchial cartilages. (D′-E′′,G′) Confocal images (lateral view, anterior to the left) of 26hpf genetic chimeras labeling donor cells with either Alexa 568 dextran (D′,D′′), Alexa 488 dextran (E′,E′′) or the sox17:dsred transgene (G′). Arrowheads indicate endodermal pouch contribution, whereas arrows indicate endoderm failing to contribute to the pouches; insets show transgene expression with bright-field image. All embryos were heat shocked at 39°C for 1h at 10hpf. (A) Heat-shocked hs:dnBmpr1a-GFP embryos have severe craniofacial defects. (B) Control wild-type endoderm transplants do not disrupt craniofacial development. (D-D′′) Transplanting wild-type endoderm into a heat-shocked hs:dnBmpr1a-GFP embryo completely rescues craniofacial development (n=15/16). (E-E′′, arrows) Heat-shocked hs:dnBmpr1a-GFP donor cells are excluded from the pouches and fail to induce viscerocranial defects in wild-type embryos. (C) No rescue occurs when donor cells fail to populate the endoderm (n=6/6). (F) sox32 mutants lack endoderm and lose all of the viscerocranium. (G,G′) Heat-shocked hs:dnBmpr1a-GFP endoderm does not rescue sox32 mutants (n=6/6). Cartilages: Mc, Meckel′s; Ch, ceratohyal; Cb′s, ceratobranchial; Pq, palatoquadrate; HM, hyomandibular. Scale bars: 100µm in A-G; 50µm in D′-E′′,G′.