Spatially varying cis-regulatory divergence in Drosophila embryos elucidates cis-regulatory logic

Both cis- and trans-acting changes could accumulate and participate in complex interactions, so to isolate the cis-regulatory component of patterning evolution, we measured allele-specific spatial gene expression patterns in Drosophila melanogaster × D. simulans hybrid embryos. RNA-seq of cryosectioned slices revealed 55 genes with strong spatially-varying allele-specific expression, and several hundred more with weaker but significant spatial divergence. Combined with mathematical modeling and regulatory locus editing, we determine the SNP responsible for the allele-specific expression observed in the gene hunchback. Embryonic mRNA profiles of mid-stage 5 hybrid and parental embryos were generated using RNA-seq