Figure 4. The Hippo pathway regulates expression of the key crystal cell fate determinant, Lozenge.
A–B) A primary third instar larval lymph gland (A–A″) and eye-antennal disc (B–B″) harbouring clones of tissue expressing UAS-yki transgenes (marked by GFP in green). Expression of Lz (greyscale in A and B, red in merged image B″) and Yki (red in A″) are shown. Ectopic expression of Lz was induced by yki overexpression in both lymph glands (indicated by arrowhead in A–A″) and eye-antennal discs (indicated by arrowheads in B–B″). Asterisks mark endogenous Lz expression in the lymph gland (A–A″) and the posterior region of the eye-antennal disc (B).
(C) lz expression, as reported by a 1.5kb region of the lz promoter fused to the lacZ gene, in a wing imaginal disc expressing UAS-yki in the posterior domain under the control of en-gal4. lz expression is greyscale in the single channel (C) and red in the merged image (C″), while UAS-yki expression is marked by co-expression of UAS-GFP (green in C′ and C″).
(D) Schematic of the lz gene locus showing conserved Sd sites, the lz-lacZ reporter, the lz reporters (pink) and the ChIP-qPCR amplicons (turquoise).
(E) Reporter assays demonstrate that several regions of the lz locus that bear conserved Sd sites can mediate transcriptional activation by Sd/Yki in Kc167 cells. When these conserved Sd sites were mutated (“m”), this activation was suppressed or abolished. The vg and fng reporters serve as negative controls.
(F) ChIP-qPCR validates binding of endogenous Yki to several of these reporter regions in Kc167 cells, particularly to the R1 region. Yki did not associate with the control region lacking Sd sites.
Scale bars = 20μm. See also Figures S3 and S4.