Spalt-related is a catabolic switch activated by prolonged starvation

Inhibition of anabolic processes during nutrient deprivation is a critical stress response necessary for survival. However, how transient vs. prolonged nutrient deprivation is sensed by the key metabolic organs and which downstream pathways mediate metabolic regulation under these conditions remain insufficiently understood.

Here we uncover an unexpected role for the transcription factor Spalt-related (Salr), a known to be involved in wing morphogenesis, as a regulator of growth and metabolism upon nutrient starvation. Specifically, we observed that Salr is necessary and sufficient to inhibit cellular and organismal growth as well as lipid storage in the Drosophila fat body. Our results indicate that Salr inhibits anabolic processes through the regulation of mTOR complex 1 activity as well as by directly controlling genes involved in lipid catabolism and autophagy.