Natural variation in sugar tolerance. Drosophila

How genetic control of metabolism contributes to evolution of animal diet choice remains poorly understood. We have addressed this by analyzing Drosophila simulans and sechellia, recently diverged species with differential diet choice. D. sechellia larvae, specialized to a nutrient scarce Morinda fruit, did not survive on sugar-rich diet, while the generalist D. simulans was sugar tolerant. Sugar tolerance in D. simulans was a tradeoff for performance on a low energy diet and it was associated with global reprogramming of metabolic gene expression. Hybridization by phenotype-based introgression revealed that genomic regions in D. simulans chromosome arm 2R were sufficient for sugar tolerance. Within these regions genes involved in the mitochondrial ribosome and intracellular signalling, such as PPP1R15/Gadd34 and SERCA, contributed to sugar tolerance. In these signalling genes, coding and regulatory genomic variations were identified, respectively. In conclusion, genomic variation in genes involved in global metabolic regulation defines species-specific macronutrient space.