TY - JOUR T1 - Adaptive evolution of proteins expressed in late and post-embryonic development in animals JF - bioRxiv DO - 10.1101/161711 SP - 161711 AU - Jialin Liu AU - Marc Robinson-Rechavi Y1 - 2017/01/01 UR - http://biorxiv.org/content/early/2017/07/10/161711.abstract N2 - Both the early conservation and hourglass Evo-Devo models suggest that, during development, late development (after the ‘phylotypic’ period: late and post-embryonic development) has the highest divergence at the morphological and molecular levels between species. Our aim here is to determine as much as possible the relative contributions of relaxation of purifying selection vs. increase in positive selection, in the observed high sequence divergence of genes from late development. For this, we investigated the evidence of positive selection on protein-coding genes in relation to their expression over development, in D. rerio, M. musculus and D. melanogaster. First, we found that genes specifically and highly expressed in late development or adult have stronger signals of positive selection. Second, genes with evidence for positive selection trend to be expressed in late development and adult. Finally, genes involved in pathways with cumulative evidence of positive selection have higher expression in late development and adult. Overall, there is a strong and consistent signal that positive selection mainly affects genes and pathways expressed in late development and adult. Our results imply that evolution of embryogenesis is mostly conservative, with most adaptive evolution affecting post-embryonic gene expression, and thus post-embryonic phenotypes. This is consistent with the diversity of environmental challenges to which juveniles and adults are exposed. ER -