Fig. 1. SYS-1 is required for the activation of Wnt target genes in E and gut formation. (A-D) Micrographs of C. elegans embryos carrying the Psdz-23::gfp::H2B transgene, in wild-type, sys-1(RNAi) or pop-1(zu189) backgrounds. Embryos are shown at the two MS, two E stage, as DIC (C,D) and corresponding nuclear GFP::H2B fluorescence (A,B) images. Wild-type (left of the dashed line) and RNAi/mutant embryos (right of the dashed line) were imaged together. Note reduced GFP fluorescence in sys-1(RNAi) and pop-1(zu189) embryos as compared with wild-type embryos. Four GFP-positive cells were observed in pop-1(zu189) embryos owing to derepression in the MS lineage. (E-G) Representative wild-type, sys-1(RNAi) and pop-1(zu189) embryos from A-D showing reporter GFP expression. (H-K) Terminally differentiated sys-1(RNAi) (H,I) or teIs3(P_med-1gfp::pop-1); sys-1(RNAi) (J,K) embryos shown under DIC (H,J) or birefringence optics revealing intestinal-specific gut granules (white speckles in I,K). Embryos lacking gut granules are outlined in white. Scale bars: 20 µm.