Changes in regulatory sequences can underlie evolutionary differences

The evolution of gene regulation and morphology in the case shown is due to evolution in cis-acting regulatory sequences. (a) In spotted fruit flies, the Yellow pigmentation protein is expressed at high levels in cells that will produce large amounts of melanin. (b) The yellow locus of Drosophila species contains several discrete cis-acting regulatory elements (red) that govern yellow transcription in different body parts. Exons are shown in gold. Arrows indicate the point of the start and direction of transcription of the gene. (c) The “wing” regulatory element from D. biarmipes drives reporter-gene expression in a spot pattern in the developing wing, whereas the homologous element from the unspotted D. melanogaster does not drive a spot pattern of reporter expression. This difference in wing cis-acting-regulatory-element activities demonstrates that changes in the cis-acting-regulatory-element function underlie differences in Yellow expression and pigmentation between the two species.