Energy demand and the context-dependent effects of genetic interactions

Abstract

word count: 170 Main text word count: 4954 Figures: 3 main and 2 supplemental Tables: 1 main and 8 supplemental 2 ABSTRACTGenetic effects are often context dependent, with the same genotype differentially affecting phenotypes across environments, life stages, and sexes. We used an environmental manipulation designed to increase energy demand during development to investigate energy demand as a 5 general physiological explanation for context-dependent effects of mutations, particularly for those mutations that affect metabolism. We found that increasing the photoperiod during which Drosophila larvae are active during development phenocopies a temperature-dependent developmental delay in a mitochondrial-nuclear genotype with disrupted metabolism. This result indicates that the context-dependent fitness effects of this genotype are not specific to the effects 10 of temperature and may generally result from variation in energy demand. The effects of this genotype also differ across life stages and between the sexes. The mitochondrial-nuclear genetic interaction disrupts metabolic rate in growing larvae, but not in adults, and compromises female, but not male, reproductive fitness. These patterns are consistent with a model where contextdependent genotype-phenotype relationships may generally arise from differences in energy 15 demand experienced by individuals across environments, life stages, and sexes.