It is known that Drosophila larvae exhibit nutrient-dependent regulation of growth during development, with some nutrients exerting sex-specific effects on body size. Now, Elizabeth Rideout and colleagues report that a low-sugar diet enhances Drosophila body size in both males and females, but that this occurs via sex-specific mechanisms. They first show that lowering dietary sugar promotes an increase in growth rate and body size in both sexes. They further report that a low-sugar diet augments insulin/insulin-like growth factor signalling pathway (IIS) activity in males by increasing insulin sensitivity, with this increase being required for the low-sugar-induced increase in body size. In females, by contrast, IIS activity and insulin sensitivity are unaffected by a low-sugar diet. Analysis of transcriptional changes reveals that a low-sugar diet also causes distinct transcriptional responses in each sex. For example, genes associated with FoxO signalling are downregulated in males, whereas female-specific transcriptional changes are consistent with a possible role for TOR. In line with this, the authors demonstrate that TOR plays a female-biased role in regulating the responses to a low-sugar diet. Overall, these findings highlight the importance of including both sexes in larval growth studies as different mechanisms may underlie similar phenotypic responses.
