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Comparison of the Coding Sequence of raptor in 27 Drosophila Species

Leon Laskowski, Brittany Cook, Jacqueline Wittke-Thompson, PhD, Department of Natural and Health Sciences, University of St. Francis, 500 Wilcox St., Joliet Il, 60435

Drosophila is a model organism used to studyt the insulin pathway as this pathway is highly conserved across eukaryotes, including molecular components and physiological responses. D. melanogaster was one of the first species to have a completely sequenced genome available. Raptor (RPTOR) binds with additional proteins to form TOR-C1, which activates (or inhibits) many proteins downstream of the insulin signaling pathway. If there is selective pressure maintaining the function of RPTOR, then the structure of the raptor gene will be highly similar between Drosophila species and will not change with increasing evolutionary distance from D. melanogaster. The raptor ortholog was identified and its CDS (Coding DNA Sequence) in 27 Drosophila species were annotated using Flybase, NCBI Blast and GEP UCSC Genome Browser, and verified using Gene Model Checker. The CDS of the raptor ortholog for 19 of the 27 Drosophila species were analyzed for conservation in the coding DNA alignment using Multipipmaker. Species closer to D. Melanogaster had higher percent identity (D. sechellia 98.3%) than species more distantly related (D. busckii 65.9%). Across all Drosophila  species, three highly conserved regions (Raptor N-terminal domain, HEAT repeat motifs, and WD40 repeat motifs) were identified. These regions have been shown to be essential for protein-protein interaction with the TOR-C1 complex. Although overall percent identity decreased as evolutionary distance increased, structural and functionally essential regions within Drosophila were not strongly influenced by evolutionary distance. Therefore, selective pressure likely maintained the function of RPTOR due to its importance in the insulin signaling pathway.

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