A conserved trans-regulatory landscape for scute expression on the notum of cyclorraphous Diptera.

Bristles on the notum of many cyclorraphous flies are arranged into species-specific stereotyped patterns. The positions of bristles correlate with differences in the spatial expression of the scute (sc) gene in those species examined so far. However, a major upstream activator of scute, Pannier (Pnr), is expressed in a conserved domain over the entire medial notum. Here we examine the expression patterns in Calliphora vicina of stripe (sr), u-shaped (ush), caupolican (caup) and wingless (wg), genes known to modify the activity of Pnr or to act downstream of Pnr in Drosophila. We find that, with minor differences, their expression patterns are conserved. This suggests that the function of a trans-regulatory network of genes is relatively unchanged in derived Diptera and that many differences are likely to be due to changes in cis-regulatory sequences of scute.