GATA5 is required for stable specification of heart and liver precursors and is sufficient to directly induce Hex. A: GATA5 MOs (20/32 embryos for G5 (5 ng) and 14/25 embryos for G5UTR (50 ng) showed reduced expression), but not GATA4 MOs (19/19 embryos for G4 (50 ng) and 22/22 embryos for G4SP (100 ng) expressed Nkx2.5) or GATA6 MO (10 ng; 14/14 embryos with normal expression), cause early deficiency of heart precursors at st. 22 (arrowheads in A1-3). Heart field was revealed by Nkx2.5 expression. Ventral views are shown, with anterior at the top. B: Liver precursors in anterior endoderm (see Additional File 3) expressing Hex are affected by 10 ng of G5 MO (31/39), but not by 50 ng of C1 MO (20/23 normal). Embryos injected uniformly are shown before (B1,3) and after (B) staining for lineage tracer (pink). Ventral views are shown, with anterior to the left. C: G4SP MO does not effect Hex expression. Embryos injected with indicated MOs were analysed at st. 22 for expression of Hex, splicing out of exon 4 of GATA4 and for ODC by RT-PCR. D: GATA5-GR induces expression of Hex mRNA in animal caps explants in the presence or absence of cycloheximide (Chx), which was added at st. 9. All samples were treated with dexamethasone at the same time to activate GATA5-GR protein. E-st. 11 control embryos.