Cis-regulatory evolution that caused change in wingless expression pattern associated with wing pigmentation pattern of Drosophila

Genetic mechanisms underlying the acquisition of new traits are an important topic in evolutionary developmental biology. Especially, the co-option of important regulatory genes potentially plays an important role in the gain of new traits. However, how the co-option occurs at the sequence level is still elusive. Drosophila guttifera has a unique wing pigmentation pattern and this is newly gained via the evolution of the expression pattern of wingless, which induces the pigmentation pattern formation. In this study, to reveal the changes in the cis-regulatory sequence which caused the co-option of wingless that lead to the expression in a new place, we conducted transgenic EGFP reporter assays of altered cis-regulatory sequences. As a result, the sequence was divided into regions needed to activate expression in the entire wing veins and a region required for repressing expression in excess parts. Comparisons with the homologous sequence of Drosophila melanogaster showed that the repressive function of the cis-regulatory region is also possessed by D. melanogaster while the activating function is newly gained in a lineage leading to D. guttifera. Furthermore, a putative binding site of SMAD transcription factors is shown to be essential for activating expression but also existing in the homologous region of D. melanogaster. Our results suggest that the pre-existing regulatory sequences in the cis-regulatory region coordinate with the newly gained sequences to acquire the new expression pattern of wingless. Graphical Abstract O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY C_FIG_DISPLAY