STRUCTURE AND EVOLUTION OF A PAIR-RULE INTERACTION ELEMENT : RUNT REGULATORY SEQUENCES IN D. MELANOGASTER AND D. VIRILIS

Abstract Pair-rule genes serve two important functions during Drosophila development: they first initiate periodic patterns, and subsequently interact with each other to refine these patterns to the precision required for definition of segmental compartments. Previously, we described a pair-rule input region of the runt gene. Here we further characterize this region through the use of reporter gene constructs and by comparison with corresponding sequences from Drosophila virilis . We find that many but not all regulatory properties of this `7-stripe region' are functionally conserved. Moreover, the similarity between these homologous sequences is surprisingly low. When compared to similar data for gap gene input elements, our data suggest that pair-rule target sequences are less constrained during evolution, and that functional elements mediating pair-rule interactions can be dispersed over many kilobases.