Figure 6

The induction of dMyc (dm) increases terminal branching and activates crp expression. (A) The terminal branches of DB (i, iii, and v) and LG (ii, iv, and vi) of L3 larvae were observed. Ectopic expression of dMyc in terminal cells with bs-Gal4 resulted in the formation of excessive and tortuous terminal branches of the DB (iii) and LG (iv) compared with those of larvae without UAS-dm (i and ii). Depletion of endogenous c-MYC by expressing siRNA against dm induced truncation of both DB (v) and LG (vi). The scale bar indicates 200 μm. (B) dMyc induced crp promoter activity. S2 cells transfected with the plasmid expressing firefly luciferase gene downstream of the crp promoter fragment, the plasmid expressing dMyc or dMyc without the DNA binding region (DN-dMyc), and the Renilla luciferase expressing plasmid (as transfection control) for 48 hours and then harvested for reporter gene assays. The ratio of firefly luciferase to Renilla luciferase luminescence signal was calculated and fold changes of luciferase activity relative to vector control are shown. Values are represented as mean ± SEM from four independent experiments. ** indicates p value <0.01, *** indicates p value <0.001. (C) Overexpression of dMyc in larvae with the genotype hs-Gal4; UAS-dMyc was observed after exposing the larvae to 35°C for 20 min. Crp, dMyc, and actin were visualized by Western blots using their specific antibodies.