RESUMEN
Drosophila sechellia is a dietary specialist fruit fly that evolved from a generalist ancestor to specialize on the toxic fruit of Morinda citrifolia This species pair has been the subject of numerous studies where the goal has largely been to determine the genetic basis of adaptations associated with host specialization. Because one of the most striking features of M. citrifolia fruit is the production of toxic volatile compounds that kill insects, most genomic studies in D. sechellia to date have focused on gene expression responses to the toxic compounds in its food. In this study, we aim to identify new genes important for host specialization by profiling gene expression response to 3,4-dihydroxyphenylalanine (L-DOPA). Recent work found it to be highly abundant in M. citrifolia, critical for reproductive success of D. sechellia, and supplementation of diet with the downstream pathway product dopamine can influence toxin resistance phenotypes in related species. Here we used a combination of functional genetics and genomics techniques to identify new genes that are important for D. sechellia ecological adaptation to this new niche. We show that L-DOPA exposure can affect toxin resistance phenotypes, identify genes with plastic responses to L-DOPA exposure, and functionally test an identified candidate gene. We found that knock-down of Esterase 6 (Est6) in a heterologous species alters toxin resistance suggesting Est6 may play an important role in D. sechellia host specialization.