Maternal loss of gpx4b promotes dorsal organizer development and depletion of gpx4b increases Wnt/β-catenin activity. (A) Expression of dorsal organizer markers chd and gsc mRNA in each indicated group of embryos at 4.3 hpf, as assessed by whole-mount in situ hybridization. Upper panels are animal pole views with dorsal towards the right. Arrows indicate the edges of the chd and gsc mRNA expression domains. Lower panels are dorsal views with animal pole upwards. The frequency of embryos with the indicated patterns is shown in the bottom right corner of each group. (B) Quantification of the arc of marker expression shown in A. (C) The expression levels of boz, chd and sqt mRNA in each indicated group of embryos at 4.3 hpf, as analyzed by qRT-PCR. (D) Expression of direct zygotic Wnt markers cdx4, sp5l and tbx6 in MZallele1 mutants and wild-type embryos at 80% or 90% epiboly stage (9 hpf). Asterisks indicate the edges of the indicated mRNA expression domains. Lateral views with dorsal towards the right and animal pole upwards. (E) The mRNA expression levels of indicated zygotic Wnt direct target genes in wild-type and MZallele1 mutant embryos at 8 hpf analyzed by qRT-PCR. (F) MZallele1 mutants show increased endogenous Wnt signaling. Values are means±s.e.m. (n=3). *P<0.05; **P<0.01; ***P<0.001. Unpaired t-test, two-tailed. Scale bars: 200 µm.