Figure 7.

Molecular evolutionary analysis of the MRS. (A) Map of the yellow locus of D. melanogaster showing the start of transcription at +1 bp, and y mutant landmarks at −300 and −91 bp. Deletion of the region between −300 and −91 bp (solid black MRS line) reduces male mating success to null-allele levels. Insertions within the region between −300 and +1 bp (solid plus dashed MRS line) significantly reduce male mating success to varying degrees. The blue square demarcates a highly conserved 35-bp sequence from −214 to −180 bp. (B) The 105-bp sequence from D. melanogaster and D. virilis, which shows the 35-bp conserved sequence in detail. This sequence is 85.7% identical between the species. The representative 35 bp immediately upstream and downstream of the sequence of interest is poorly conserved with 31.4% and 22.9% identity, respectively. The purple rectangle demarcates a putative Dorsal transcription factor binding sequence. This consensus sequence was identified using the web-based program TFSEARCH, which utilizes the TRANSFAC database (see Thisse et al. 1991; Akiyama 1998; Heinemeyer et al. 1998). The three green rectangles demarcate three putative DSX-binding sites, two of which overlap the putative Dorsal site. Consensus DSX sequences are from Erdman et al. (1996). (C) Alignment of the conserved 35-bp sequence across 12 Drosophila species. The right column indicates percentage identity of sequence. The (*) indicates that the percentage identity calculated does not include the 22-bp insertion in the marked species. Across the Drosophila species that we analyzed, there is only a single base change in the putative Dorsal-protein-binding site, in D. novamexicana. The putative Doublesex-protein-binding sites are perfectly conserved across all the species in our analysis.