Fig. 7. Ectopic DMyb activity inhibits endoreduplication and growth in salivary glands. (A,B) Fluorescent micrographs of salivary glands dissected from (A) fkh-Gal4/UAS-GFP and (B) sd-Gal4/UAS-GFP third instar larvae show that both Gal4 lines drive expression in endocycling salivary gland cells (sg), but not in fat body (fb) or imaginal ring cells (ir), which are shown in an inset at higher magnification. (C) Graphical representation for each indicated genotype of the average ratio of the DNA signal from ‘expressing’ salivary gland nuclei to non-expressing fat body nuclei [using the method of Weiss et al. (Weiss et al., 1998)]. Standard deviations are shown. (D-H) DNA staining of salivary glands and representative nuclei from larvae that were approximately 120 hours AED. Genotypes were: (D) sd-Gal4/+ control; (E) sd-Gal4/UAS-DMyb; (F) sd-Gal4/UAS-DMyb; (G) sd-Gal4/UAS-DMyb; HS-dE2F, HS-dDP/+, which had been subjected to a 30 minute heat-shock treatment every 24 hours after collection; and (H) sd-Gal4/UAS-RBF. Panels from left to right show the relative sizes of complete glands and (at a higher magnification), relative sizes of imaginal ring nuclei (ir), fat body nuclei (fb) and salivary gland nuclei (sg) that represent the mean for each genotype. The DNA signal ratio of that nucleus to the average fat body nucleus indicated. (I,J) DNA staining of salivary glands from (I) sd-Gal4/UAS-DMyb and (J) sd-Gal4/UAS-DMyb; HS-dE2F, HS-dDP/+ larvae, which had been subjected to 30 minute heat-shock treatments every 12 hours after collection, and which were 144 hours AED. Arrowhead in J indicates enlarged fat body nuclei resulting from excess endoreduplication in these cells driven by HS-dE2F/DP. Scale bars: in A, 0.1 mm for A,B; in A (inset), 0.025 mm for A,B; in D, 0.1 mm (low magnification) for D-J; in D, 0.025 mm (high magnification) for D-H.

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