Meeting Abstract
Many traits vary with regard to sex as well as nutrition. Yet, the mechanisms regulating this plasticity over development are not well understood. In insects, two different pathways are involved in how morphological development responds to nutrition and sex. The insulin signaling pathway informs an organism of its nutrient conditions while doublesex regulates sex determination. Recent evidence suggests there may be links between these pathways in regulating sexual dimorphism. In this study, we investigate the hypothesis that sex-specific responses to nutrition are mediated by insulin signaling interactions with doublesex. We use the monarch butterfly (Danaus plexippus) as a study system because high and low nitrogen leaves occur naturally on their host plant, the milkweeds (Asclepias), and because they have a sequenced and annotated genome and well-studied sexual dimorphism. Wild-collected larvae were raised on either a high or low nitrogen diet from the second instar to pupation. Wing and brain tissue was dissected four days after pupation and total RNA was extracted. q-RT-PCR was used to measure relative levels of expression in insulin-like peptide 1 (ILP-1), insulin-like receptor, FOXO, and doublesex. We predicted that 1) larval diet quality would cause variation in gene expression in a sex-specific way and 2) links between pathways would be represented by concordant variation in doublesex expression and all insulin-pathway genes. Understanding the mechanisms that mediate the interaction of nutrition and sex during development has implications for the dynamics of sexual selection and for clarifying the molecular pathways through which organisms differentially allocate resources.
