Figure 2. dHNF4 null mutants are sensitive to starvation.

(A) A schematic representation of the dHNF4 locus is depicted, with the gene structure shown below along with three 3′-flanking genes, CG9298, CG9296, and CG9289. The locations of the two P-element insertions in dHNF4, EP2449 and KG08976 are shown, along with the dHNF4^Δ17 and dHNF4^Δ33 deletions. (B) A time course of the viability of starved control and dHNF4 mutant larvae, with and without a wild type hs-dHNF4 transgene. Whereas most larvae that are transheterozygous for precise excisions of the EP2449 and KG08976 P-elements (control) can survive two days of starvation, most dHNF4^Δ33/dHNF4^Δ17 mutants (dHNF4⁻) die. Heat treatment (+hs) has no effect on these animals. Heat treatment of dHNF4^Δ33/dHNF4^Δ17 mutants that carry a hs-dHNF4 rescue construct (hs-dHNF4, dHNF4⁻ +hs), however, regain their starvation resistance. (C) Control (cont) or dHNF4 mutant (dHNF4⁻) late second instar larvae were either maintained on moist filter paper or on a 20% sucrose diet (sucrose) for two days at 25°C, after which the percent of surviving animals was scored and plotted. Whereas dHNF4 mutant larvae are sensitive to starvation, they survive normally on a sucrose diet. A representative of four independent experiments is presented, with N=10–40 animals in each experiment. Error bars are +/− S.E. * p = 1.3×10⁻³.