PT - JOURNAL ARTICLE AU - Sebastian Kittelmann AU - Alexandra D. Buffry AU - Isabel Almudi AU - Marianne Yoth AU - Gonzalo Sabaris AU - Franziska A. Franke AU - Juan Pablo Couso AU - Maria D. S. Nunes AU - Nicolás Frankel AU - José Luis Gómez-Skarmeta AU - Jose Pueyo-Marques AU - Saad Arif AU - Alistair P. McGregor TI - Gene regulatory network architecture in different developmental contexts influences the genetic basis of morphological evolution AID - 10.1101/219337 DP - 2017 Jan 01 TA - bioRxiv PG - 219337 4099 - http://biorxiv.org/content/early/2017/11/14/219337.short 4100 - http://biorxiv.org/content/early/2017/11/14/219337.full AB - Convergent phenotypic evolution is often caused by recurrent changes at particular nodes in the underlying gene regulatory networks (GRNs). The genes at such evolutionary ‘hotspots’ are thought to maximally affect the phenotype with minimal pleiotropic consequences. This has led to the suggestion that if a GRN is understood in sufficient detail, the path of evolution may be predictable. The repeated loss of larval trichomes among Drosophila species is caused by the loss of shavenbaby (svb) expression. svb is also required for development of leg trichomes, but the evolutionary gain of trichomes in the ‘naked valley’ on T2 femurs in Drosophila melanogaster is caused by the loss of microRNA-92a (miR-92a) expression rather than changes in svb. We compared the architectures of the larval and leg trichome GRNs to investigate why the genetic basis of trichome pattern evolution differs in these developmental contexts. We found key differences between these two networks in both the genes employed, and in the regulation and function of common genes. These differences in the GRNs reveal why mutations in svb are unlikely to contribute to leg trichome evolution and how instead miR-92a represents the key evolutionary switch in this context. Our work shows that differences in the components and wiring of GRNs in different developmental contexts, as well as whether a morphological feature is lost versus gained, influence the nodes at which a GRN evolves to cause morphological change. Therefore our findings have important implications for understanding the pathways and predictability of evolution.Significance Statement A major goal of biology is to identify the genetic cause of organismal diversity. Convergent evolution of traits is often caused by changes in the same genes - evolutionary ‘hotspots’. shavenbaby is a ‘hotspot’ for larval trichome loss in Drosophila, however microRNA-92a underlies the gain of leg trichomes. To understand this difference in the genetics of phenotypic evolution, we compared the underlying gene regulatory networks (GRNs). We found that differences in GRN architecture in different developmental contexts, and whether a trait is lost or gained, influence the pathway of evolution. Therefore hotspots in one context may not readily evolve in a different context. This has important implications for understanding the genetic basis of phenotypic change and the predictability of evolution.