The identification of the molecular changes responsible for morphological variation is still one of the main challenges in evolutionary biology. Furthermore, it is completely unclear, how such molecular changes influence the gene regulatory networks (GRNs) underlying organ development. To answer these questions, we study natural variation in head and eye development in the two closely related Drosophila species, D. melanogaster and D. mauritiana.
We applied geometric morphometrics to show that these species show clear natural variation in size and shape of their compound eyes and head structures. A comparative RNA-seq analysis of head development in combination with existing transcription factor binding data was used to identify differentially expressed genes and central transcription factors that may explain these morphological differences.
We found that the GATA transcription factor Pannier (Pnr) regulates many differentially expressed genes and might represent one of the flexible nodes in the head developmental GRN. Since pnr itself is differentially expressed, its regulatory region could have evolved between the two species. To reveal head-specific regulatory elements and interspecific differences in chromatin accessibility, we applied ATAC-seq. This data will help us determining the genomic locus responsible for the extensive remodeling of the transcriptomic landscape downstream of Pnr.