Abstract
Development of the Drosophila melanogaster central nervous system midline depends on the gene single-minded (sim). Although sim regulation has been studied extensively, the fact that an enhancer mediating late embryonic sim transcription has not been identified suggests that additional regulatory sequences remain unknown. We tested several evolutionarily conserved sequences in the sim downstream region and isolated sim_3pB , whose midline activity in a reporter gene assay begins later than previously characterized sim enhancers. Its activity shares several key similarities with the Aedes aegypti sim _ 5P3 enhancer, though is sufficiently different to warrant further investigation into how sim_3pB functions in its native context.
