Figure 1

Dpp signaling in the third instar eye-antennal disc. Posterior is to the right and dorsal uppermost in all preparations. (A) Nuclear Brk protein was detected only in parts of the dorsal antennal disc and a few cells at the very anterior of the eye disc proper (arrows); (B) Nuclear Brk protein is strongly detected in peripodial membrane cells. There is a high-to-moderate gradient from ventral-to-dorsal; (C) A positive target of BMP signaling, DadLacZ, was active from 5-6 cell diameters anterior of the morphogenetic furrow and more posteriorly. Arrowhead indicates the morphogenetic furrow. Expression begins slightly earlier (more anteriorly) near the disc margin; (D) DadLacZ was detected in the peripodial epithelium over the ventral antennal disc; (E) Phosphorylated Mad protein is detected in nuclei in a broad domain centered on the MF, extending only slightly more anteriorly at the disc margin, and in a stripe of cells posterior to the furrow. Arrowhead indicates the morphogenetic furrow. Weak labeling of photoreceptor cells in the posterior of the disc is non-specific, since it is unaffected in Mad mutant cells (not shown); (F) Phosphorylated Mad is absent from the peripodial epithelium apart from a few cells dorsally; (G) The Dpp-LacZ transgene is expressed within the morphogenetic furrow (magenta), overlapping the domain of Mad phosphorylation (green). It is possible that Dpp-LacZ might lag behind endogenous Dpp protein; (H) Dpp-LacZ; (I) pMAd; (J) profile plot of the pMad labeling shown in panel I; (K) Profile plot of the Dpp-LacZ shown in panel H. (L) An eye disc labeled with phosphorylated Mad (green) and Cyclin B (magenta) shows that the cells posterior to the furrow where Phospho-Mad levels peak also express the Cyclin B associated with the SMW; (M) Profile plots of the CycB and pMad levels from panel L. (N) A close up of a single confocal z-plane, doubly labeled with CycB and pMad like that shown in panel L. Strongly pMad-positive cells are also labeled with CycB (arrows in panels O, P); (O) pMad labeling from panel N. (P) CycB labeling from panel N. (Q) pMad labeling of an eye disc; (R) Profile plot of the labeling shown in panel Q; (S) A 5 micron strip from panels Q & R, magnified and re-projected to show pMad labeling (green) from the side. Apical disc surface uppermost. Nuclei of all cells are labelled with DRAQ5 (magenta); (T) pMad labeling from panel S; (U) DRAQ5 labeling of all nuclei from panel S; (V) A profile plot from the lateral region of an eye imaginal disc.