Low FoxO expression in Drosophila somatosensory neurons protects dendrite growth under nutrient restriction

Abstract

During prolonged nutrient restriction, developing animals redistribute vital nutrients to favor brain growth at the expense of other organs. In Drosophila, such brain sparing relies on a glia-derived growth factor to sustain proliferation of neural stem cells. However, whether other aspects of neural development are also spared under nutrient restriction is unknown. Here we show that dynamically growing somatosensory neurons in the Drosophila peripheral nervous system exhibit organ sparing at the level of arbor growth: Under nutrient stress, sensory dendrites preferentially grow as compared to neighboring non-neural tissues, resulting in dendrite overgrowth. Underlying this neuronal nutrient-insensitivity is the lower expression of the stress sensor FoxO in neurons. Consequently, nutrient restriction suppresses Tor signaling less and does not induce autophagy in neurons. Preferential dendrite growth is functional desirable because it results in heightened animal responses to sensory stimuli, indicative of a potential survival advantage under environmental challenges.