The gustatory system influences "Drosophila" lifespan

The lifespan of an organism is affected by the complex interplay between genetic and environmental factors. In C. elegans, this interaction between genes and environment is mediated by the sensory system. Indeed, a subset of gustatory and olfactory neurons has been shown to inhibit worm longevity, while a different subset of gustatory neurons promotes longevity. While olfactory neurons have been found to affect lifespan through signals coming from the worm’s reproductive system, the lifespan effects of gustatory neurons are shown to be mediated by the insulin/IGF-1 signaling (IIS) pathway. Recently, the effects of olfaction on lifespan have been reported in Drosophila, which suggests that other aspects of the sensory influence on lifespan will also be conserved between these two species. For my thesis, I show that gustatory inputs not only affect Drosophila lifespan but that they also do so in a bidirectional manner. Interestingly, I find that fly gustatory inputs influence lifespan independent of the level of food intake. Indeed, compared to controls, taste-impaired flies have an increase in feeding rates and body weights and show no decrease in lipid storage. Moreover, I show that the gustatory influence on fly lifespan is dependent on food type, i.e., this influence depends partly on yeast in the food source, which suggests that the gustatory system affects longevity in response to a number of food-derived cues. Consistent with the above hypothesis, I find that the gustatory system affects lifespan partly in parallel to the IIS pathway. I show that taste inputs shorten Drosophila lifespan through inhibition of the IIS pathway effector dFOXO, while other taste inputs lengthen lifespan via a different pathway that acts in parallel to dFOXO. These data suggest that different gustatory cues will modulate the activities of distinct molecular pathways, one of which is IIS, to optimize the animal’s survival under different environments.The findings that the gustatory and olfactory influences on lifespan exist in bothC. elegans and Drosophila raise the intriguing possibility that mammalian lifespan is also subject to the activities of the sensory system. Indeed, in mammals both gustatory and olfactory information are relayed to the hypothalamus, a region in the brain that controls neuroendocrine function and physiology. Thus, the processing of this sensory information by the hypothalamus may consequently affect lifespan.