Research

Vinegar flies (genus Drosophila) utilize a wide variety of food resources that include sap, fruits, flowers, cacti, and mushrooms. Mushroom-feeding species that occur in the immigrans-tripunctata radiation are generalists on fleshy Basidomycota mushrooms, including  edible and toxic species. These flies are among a very limited number of eukaryotes that can tolerate cyclopeptide toxins found in some species of Amanita mushrooms (e.g., destroying angels). While the toxic mushrooms make up only a small portion of their possible diet, all mushroom-feeding Drosophila that have been assayed can tolerate high concentrations of the toxins.  

Cyclopeptide toxins act by binding to RNA polymerase II, which inhibits the production of messenger RNA and leads to cell death in most multi-cellular organisms. The physiological mechanism of toxin tolerance within mushroom-feeding Drosophila is poorly understood, but we do know the flies do not have mutations  that would prevent the toxin from acting. To better characterize the physiological mechanism, we are using metabolomic and transcriptomic analyses of larvae after they are reared on diets with and without the toxin. We are analyzing the spectra generated by global NMR of two tolerant species (D. guttifera and D. recens) and one susceptible species (D. deflecta) to identify both the impact of the toxin on the larval metabolome and the manner in which the larvae metabolize it. In addition, we are comparing gene expression within D. guttifera and D. recens larvae after feeding on diets with and without toxin to identify genes that may contribute to toxin tolerance. We are expanding these analyses to include transcriptomic data for 12 tolerant and 6 susceptible species and metabolomic data for  eight tolerant species and two susceptible species with our Dimensions of Biodiversity Grant (DEB-1737869).

Expanding on our transcriptomic and metabolomic analyses of toxin tolerance, we are sequencing the genomes of tolerant and susceptible species in the immigrans-tripunctata radiation. The evolution of novel adaptations can produce changes, such as gene duplications and/or changes in the rate of molecular evolution, in the genomes of species in which they occur. We are sequencing the genomes of these species using a combination of long reads (Oxford Nanopore), short reads (Illumina HiSeq), and structural data. The construction of a hybrid, de novo assembly for each species is worked on in lab and in BIO3545-Genomics: DNA to Gene ID. We are annotating these assemblies using other Drosophila genomes and the RNAseq reads generated for each species. Once the genomes are annotated, we will examine them in a phylogenetic context to identify potential genomic signals of toxin tolerance, such as gene duplication events in detoxification gene families.