Donya Shodja, Rebeiz Lab
Investigating the developmental network of the posterior lobe, a novel morphological structure
A major challenge in studying the evolution of novel anatomical structures is deciphering how the genetic programs underlying their development initially form. Work on these morphological novelties has frequently implicated drastic changes to signaling pathways in their development and evolution. However, we generally lack an understanding of how the regulation of these pathways are altered to form new structures, and how downstream responses to signaling events evolve to shape these structures during their development. To investigate this, I study the role of Notch signaling during the evolution of a recently evolved structure, the posterior lobe, a cuticular outgrowth on the genitalia of males within the melanogaster clade. The ligand for the Notch signaling pathway, Delta, is required for posterior lobe development, and its expression has been expanded in lobe-forming species. We’ve identified a transcriptional enhancer in the Delta locus that recapitulates the endogenous expression of Delta in the posterior lobe. Comparisons of this enhancer’s activity to reporters bearing orthologous regions from non-lobed species suggests that changes have occurred upstream of Delta to expand into the lobe-forming zone. Thus, in contrast to previous examples of novelty, our results suggest that a pre-existing signaling source was expanded and recruited to generate a novel structure. I present experiments to dissect the upstream regulators of Delta and investigate downstream targets of the Notch pathway in this novel tissue. These results highlight the nuanced view of novelty that can be obtained through the comparison of closely related species at the level of gene regulatory elements.
Friday, November 9th
A219B Langley Hall