The role and evolution of the Dopa decarboxylase gene in the origin of a derived dimorphic fruit fly pigmentation trait

Understanding the genetic and molecular underpinnings for trait diversity remains a central goal of evo-devo research. Traits arise by the orchestrated expression of numerous genes in a gene regulatory network. Remaining poorly understood is how these networks and their expression patterns are initially assembled and subsequently diversify. Gene expression is controlled by DNA sequences known as cis-regulatory elements (CREs) that possess binding sites for transcription factors whose binding drives a specific pattern of expression. It is anticipated that gene expression evolution often occurs through the formation, modification, and destruction of CREs, presumably by changes that create or destroy binding sites for transcription factors. However, the binding site level of CRE evolution has been worked out in few cases. The fruit fly species Drosophila melanogaster has a male-specific pattern of abdominal pigmentation for which the enzyme encoding genes and several of their expression-regulating transcription factors are known. However, the details of how these regulators interact with CREs remain largely uncharacterized, including the Dopa decaboxylase (Ddc) pigmentation enzyme gene. Here we share the results of our efforts to uncover the CRE-basis of this gene’s expression pattern, and how this regulation and pattern of expression evolved during the origin of this male-specific trait