Meeting Abstract
Nutrition-responsive development is widespread in nature, and its underlying mechanisms are being elucidated in growing detail. Yet our understanding of how these mechanisms came to be involved in the regulation of nutritional plasticity, and their potential roles in its diversification remains modest. Here we use Onthophagus horned beetles to better understand the mechanisms and evolution of nutrition-responsive development of beetle horns, whose development is characterized by varying degrees of nutrition responsiveness. We used comparative RNAseq and RNAi to contrast and functionally investigate the formation of horns in three Onthophagus species which exhibit diverse degrees of nutrition-responsive growth, ranging from moderate (ancestral) to extreme (derived) as well as secondarily lost nutrition responsiveness. We find (i) that species with stronger morphological responses to nutrition utilize larger repertoires of differentially expressed genes, and (ii) that genes which ancestrally already possessed nutrition-responsive expression tend to evolve more elaborate nutrition-responsive profiles. Comparative functional analysis of potential regulatory genes is ongoing and includes genes and pathways whose functions in growth regulation are already well established. Among these, we identify the insulin signaling pathway as a major contributor to nutrition-responsive growth and its evolution, both within the genus Onthophagus, as well as across lineages which independently evolved horns and nutrition-responsive horn growth. By combining unbiased, genome-wide assessments with functional evaluations of candidate genes we hope to provide a more comprehensive approach in the regulation and evolution of nutrition-responsive growth development.
