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The mesodermal deltaD regulatory element requires spt and ntl function. (A-I) Stable transgenics carrying the dld reporter construct (A) express mCherry at the blastoderm margin during mid-gastrulation (G), and in the tail bud and hindbrain (C,D,H,I). Transgene expression begins by 30% epiboly (E,F; animal pole views). (J-M) Stable dld transgenics were injected with MOs targeting ntl, spt or both transcripts, and analyzed by whole-mount in situ hybridization for mCherry. Most uninjected control (J) and Ntl-depleted embryos (K) expressed mCherry [76% (38/50) and 72% (26/36), respectively]. Only 67% (22/33) of Spt-depleted embryos expressed mCherry, and only 9% (3/33) did so at a level comparable with that of uninjected controls (L). No spt+ntl MO-injected embryos (0/54) expressed mCherry (M). (N-Q) In situ hybridization revealed that endogenous dld responds to Spt and Ntl depletion in a similar manner to the transgene.
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