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. 2017 Apr 10;13(4):e1006718. doi: 10.1371/journal.pgen.1006718

Fig 7. C15 down-regulates LAE in the developing pretarsus, cell autonomously as well as non-autonomously through Bowl stabilization.

Fig 7

(A-B) Mosaic late L3 leg discs harboring C15 loss-of-function clones (GFP positive) in the presence of the LAEwt-RFP reporter. Merged GFP (green) and LAE-driven RFP (red) fluorescence together with C15 (cyan) (A) or Bowl (magenta) (B) immunostaining are shown. Boxed distalmost areas are magnified for each marker in isolation, in (A’, B’), (A”, B”) and (A”‘, B”‘), respectively. A faint LAEwt-RFP up-regulation (red arrow) is observed in mutant pretarsal cells (white arrow) situated farthest away from C15+ (GFP negative) cells, i.e., black areas in (A’) and (B’). Strongest LAEwt-RFP up-regulation is observed in C15 mutant cells without detectable nuclear Bowl (red arrows). Conversely, LAEwt-RFP expression is not observed in C15-/- cells expressing Bowl protein (magenta arrows). (C) Mosaic late L3 leg disc expressing LAE-RFP and harboring bowl-/- clones (GFP-; i.e. black areas). Merged GFP (green), C15 (cyan) and LAE-driven RFP (red) expression is shown. The boxed distalmost area is magnified for each marker in isolation, in (C’), (C”) and (C’”), respectively. LAEwt-RFP is strongly de-repressed in bowl mutant cells which does not express C15 (white arrow), whereas only a faint up-regulation is observed in pure pretarsal clones. Note that bowl activity is not required for C15 expression there. Taken together, this result indicates that C15 TF activity is not sufficient for full LAE repression in the developing pretarsus. (D) Mosaic late L3 leg disc harboring C15-/- clones (detected by the absence of RFP fluorescence; i.e., black areas are mutant for C15 here; see Materials and methods), in the presence of the LAEm3-GFP reporter. Merged RFP (red), C15 (cyan) and LAE-driven GFP (green) expression is shown. The boxed distalmost area is magnified for each marker in isolation, in (D’), (D”) and (D”‘), respectively. Note that full de-repression of Bowl-unresponsive LAEm3-GFP reporter is now observed (green arrow in D”‘) in most if not all pretarsal cells of a large C15 mutant clone (white arrow in D”), to reach expression levels equivalent to those observed in neighboring tarsal cells. (E) Epistatic relationships between C15 and bowl and their joint repressive activity on bab2 (LAE-RFP) expression through cell autonomous and non-autonomous effects.