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Fig. 8 Bmp2b and Bmp7 interact synergistically in a cellautonomous manner. (A-D) Lateral views of live 24 h.p.f. embryos of the four phenotypic classes resulting from injection of bmp mRNAs. (A) Class I embryos display wild-type morphology. (B) In class II embryos the head is slightly reduced, while the hematopoietic mesoderm is expanded (arrow). (C) Class III embryos lack head and notochord. (D) Class IV embryos acquire a spindle shape lacking obvious dorsoventral polarity. (E) Phenotypic distributions following the expression of different bmps either separately or in combination. A synergistic increase in ventralizing potential is observed following the coexpression of bmp2b or bmp4 with bmp7, but not following the coexpression of bmp2b with bmp4. (F) Separate injection of one dose of bmp2b RNA and one dose of bmp7 RNA in adjacent blastomeres (lower, left panel) does not cause an enhanced effect compared to the injection of two doses of bmp2b or bmp7 (upper panels). A cooperative effect between bmp2b and bmp7 is only observed if RNAs for both factors are coinjected in the same cell (lower, right panel).