Antagonistic pleiotropy for life-history traits at the gene expression level.

Life-history trade-offs prevent different components of fitness from being maximized simultaneously. Although the existence of trade-offs has been clearly demonstrated, the 'classical' mechanism of adaptive resource allocation that should underlie them has recently received criticism. In this study, we explore the molecular mechanisms of life-history trade-offs by applying a quantitative genomic approach. Analysis of global gene expression in Drosophila melanogaster revealed 34 genes whose expression coincided with the genetic trade-off between larval survival and adult size. The joint expression of these candidate 'trade-off' genes explained 86.3% of the trade-off. Fourteen of these genes have known functions which suggest that the larval survival-adult size trade-off could be the result of resource allocation at the organismal level, but at the level of cellular metabolism the trade-off would reduce to a shift between energy metabolism versus protein biosynthesis, regulated by the RAS signalling pathway.