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. 2001 Aug 1;15(15):1900–1912. doi: 10.1101/gad.203301

Figure 6.

Figure 6

A genetic analysis of the Imd pathway. (A) Overexpression of UAS-dTAK1 and UAS-Dredd (isoform δ*) using the UAS/GAL4 system was able to partially or completely rescue the dTAK1 and Dredd mutations, respectively (dTAK1, left panel; Dredd, data not shown). Overexpression of these two constructs with an hs-GAL4 driver induces a weak but consistent expression of the Diptericin gene after heat shock in absence of infection (right panel). By classic genetic techniques, the UAS and GAL4 constructs were placed in the imd, DmIKKβ, and DmIKKγ genetic backgrounds. The right panel shows that the Diptericin expression induced by overexpressing dTAK1 is blocked by the DmIKKβ and DmIKKγ mutations but not by the imd mutation. In contrast, Dredd-mediated expression of Diptericin is not blocked in the DmIKKγ and imd mutant backgrounds. Total RNA for Northern Blot analysis was extracted from adult flies collected 24 h after a 1 h heat shock (37°C) that carry one copy of either a UAS-dTAK1 transgene (II chromosome) or a UAS–Dredd transgene (III chromosome) and one copy of the hs-GAL4 transgene (III chromosome). In the case of Dredd, we use a recombinant line carrying both UAS-Dredd and hs-GAL4 on the same chromosome. (B) Overexpression of UAS- Dredd by the yolk-GAL4 driver induced a high level of Diptericin-lacZ activity in absence of challenge that is dependent on Relish but not the imd or the DmIKKβ genes. Unchallenged female adult flies were generated that carry one copy of a Diptericin-lacZ (X chromosome) reporter gene in combination with one copy of a UAS–Dredd transgene (X or III chromosomes) and one copy of the yolk-GAL4 driver transgene (III chromosome) in wild-type, imd, DmIKKβ, and Relish mutant backgrounds. The first column shows the genotype, and the second and third columns indicate the presence or absence (−) of the UAS-Dredd and yolk-GAL4 driver, respectively. The last column shows the level of Diptericin-lacZ expression monitored by LacZ titration (Manfruelli et al. 1999). Means for Diptericin-lacZ expression are shown with standard deviation, and the number of repeats are given in brackets. The yolk-GAL4 driver expresses GAL4 specifically in the female adult fat body. The level of Diptericin-lacZ in 6 h-challenged females was 21 (4.6; 26).