TNF and infection: When the flies were challenged with fungal spores, all the five AMP genes were highly induced in wild type flies, and the expression of these genes was strongly reduced or abolished by mutation of the Toll-dependent transcription factor, Dif. Under the same infection condition, most of the mutant flies were defective in activation of certain types of AMP gene expression, and different AMP genes appear to require different genes for their activation in response to fungal infection (Figure 4).