is necessary for avoiding saponin in .

Saponins function as a natural self-defense mechanism for plants to deter various insects due to their unpleasant taste and their toxicity. Here, we provide evidence that saponin from functions as an antifeedant as well as an insecticide to ward off insects in both the larval and the adult stages. Using a behavioral screen of 26 mutant fly lines, we show that the gene cluster plays a role in saponin avoidance in the labellum. The mutant does not avoid saponin and exhibits increased lethality when fed saponin-mixed food. Tissue-specific rescue experiments with five different isoforms revealed that only the isoform is required for saponin sensation. We propose that in contrast to sensing many other bitter compounds, saponin sensing does not require the function of core taste receptors, such as GR32a, GR33a, and GR66a. Our results reveal a novel role for GR28b in taste. In addition, the ability of saponin to act as insecticides as well as antifeedants suggests its potential application in controlling insect pests.