Fig. 5. ELT-2/GATA is sufficient for enh^A::GFP expression in non-endodermal cells activated by Notch. (A) Expression of a ref-1 family member, hlh-26, following Notch interactions in AB descendants. The embryo is at the 26-cell stage, anterior to left. Cells labeled 1 are AB descendants activated by Notch signaling beginning at the four-cell stage of embryogenesis; cells labeled 2 are AB descendants activated by Notch signaling beginning at the 12-cell stage of embryogenesis. The arrow indicates an AB descendant that does not contact any ligand-expressing cells, and so is not activated by either the first or second interaction. The asterisk here and below indicates the P4 blastomere; this blastomere is transcriptionally quiescent, and thus serves as a negative control for expression levels. (B) Lack of enh^A::GFP expression in AB descendants in wild-type embryos. Here and below, the presence of the transgene was confirmed by either Notch-dependent or Notch-independent expression at later embryonic stages. (C-H) DIC and fluorescent images of similarly oriented embryos at the same developmental stages following heat shock of ELT-2/GATA. Because cell division patterns are invariant in early C. elegans embryos, the Notch-activated AB descendants (sets 1 and 2) can be identified solely by position. (E,F) Lack of GFP expression after mutating all WGATAR sequences to WCATAR. (G,H) Lack of GFP expression after mutating all CSL sites to RAGGCAA.