Meeting Abstract
Most adult winged insects follow a highly conserved body plan which consists of an abdomen without any non-genital appendages. Sepsid flies are one of the exceptions; males of some species have modified a flat, sclerotized plate on the abdomen into a remarkable brush-like appendage that varies in shape and size across the family. These novel brushes are used to stimulate the females during courtship, are ontogenetically expensive to build and have a complex evolutionary history. Using CRISPR/Cas9, we attempt to unravel the gene regulatory network (GRN) underlying the brush in two species with morphologically distinct brushes and possible independent evolutionary origins, Themira biloba and Perochaeta dikowi. T. biloba has an elaborate brush that extends substantially from the abdomen with long, distal bristles while P. dikowi has a simple brush that is mostly flat against the abdomen with short bristles. We test four candidate genes (doublesex, abdominal-A, extradenticle and Distal-less) and show that both the limb- and sex-patterning pathways are co-opted in the development of this novel brush. In both species, doublesex and abdominal-A have been similarly co-opted into the GRN for both elaborate and simple brushes. However, in T. biloba alone, Distal-less and extradenticle are additionally necessary for brush development whereas in P. dikowi, there is no evidence for the involvement of Distal-less. This suggests that Distal-less might have been co-opted specifically in the genus Themira to facilitate the development of a more elaborate brush with large cuticular extrusions.
