Inspecting the role for the trans-regulatory landscape to the origin, diversification, and loss of a sexually dimorphic fruit fly pigmentation trait

A major goal for evolutionary-developmental biology research is to identify the genetic changes underlying the origins, diversification, and loss of morphological traits. Such traits are built by the spatial and temporal regulation of gene expression, and thus the evolution of gene expression is often involved in their evolutionary histories. Gene expression is under the control of a network of transcription factors (trans-landscape) that ultimately impinge on the cis-regulatory elements (CREs) of differentiation genes whose encoded proteins produce particular traits. Transcription factor genes are often highly pleiotropic, as they can regulate the expression of multiple genes for multiple traits. Thus, it seems reasonable to expect that evolutionary changes in gene expression more frequently occurred by mutations altering the CREs for differentiation genes than changes to the trans-landscape. Our research aims to test whether this expectation for a conserved trans-landscape applies to the origin, diversification, and loss of a well-studied fruit fly pigmentation trait in the Sophophora subgenus. The origin of a male-specific pattern of abdominal tergite pigmentation involved the gain of CREs controlling the expressions of pigmentation enzyme genes responsive to the prevailing trans-landscape of body plan patterning and sexual dimorphism transcription factors. Here, we share our results from tests of these CREs in transgenic hosts that represent the ancestral sexually monomorphic trait, diverse forms of the derived dimorphic trait, and a secondary loss of the dimorphic trait. The outcomes from these tests will reveal the extent to which this particular trans-landscape has remained conserved while the pigmentation phenotype has widely evolved