Genetics and Evolution of Gyromitrin (PhD Research)

Lorchels (Gyromitra spp.) are iconic primarily for what they are not – morels (Morchella spp.), choice edible mushrooms that are foraged and enjoyed around the world. Some lorchels contain a mycotoxin called gyromitrin, which is converted in the stomach into monomethylhydrazine, an ingredient in rocket fuel that is as bad for you as it sounds like it would be. You'd think this would be a deterrent to their consumption. However, in Finland, the deadly poisonous Gyromitra esculenta is widely consumed as a delicacy after being prepared using a tedious boiling procedure to rid it of the majority of its gyromitrin. Across the United States, especially in the Midwest, there is also a culture of consuming certain lorchel species. Some of these are anecdotally considered nontoxic, or at least less toxic than Gyromitra esculenta.

There are about 85 species in the lorchel family, but only a handful are common in Michigan. From left to right: Gyromitra ancilis, Gyromitra brunnea, Gyromitra korfii group, and Gyromitra venenata. Only G. venenata is known to contain gyromitrin.

1. Distribution of gyromitrin

Our limited understanding of which lorchel species contain gyromitrin motivated us to develop a new gyromitrin assay and to test as many lorchels as we could get our hands on, culminating in a manuscript that has recently been published in the journal Mycologia (accepted and in press, preprint available here). The main findings of our research are that gyromitrin has a discontinuous and more limited distribution than expected. We detected gyromitrin in all tested specimens of the Gyromitra esculenta group as well as Gyromitra leucoxantha, which was a surprise. This distribution is consistent with a model of horizontal gene transfer. To the delight of lorchel foragers, we did not detect gyromitrin in any tested specimens of G. brunnea, G. caroliniana, or the G. korfii group. 

The many mushrooms that were acquired for this project are contributing to taxonomical investigations. For example, specimens collected from University of Michigan's Stinchfield Woods were recently described as a new species, Gyromitra americanigigas. Your donations were invaluable in our gyromitrin work and continue to be essential for ongoing taxonomy and genomics research. We continue to look for all the help we can get crowdsourcing fungi from the family Discinaceae, which includes saucer-shaped mushrooms previously classified in the genus Discina as well as truffle-like, underground mushrooms in the genus Hydnotrya, in addition to the stipitate lorchels. Please read these instructions if you are interested in contributing!

2. Genetics of gyromitrin

Gyromitrin belongs to a rare class of compounds containing a nitrogen-nitrogen bond. Only about 0.1% of characterized secondary metabolites belong to this group. We have no idea what genes are responsible for gyromitrin production, so our next goal is to discover its genetic underpinnings. We are doing this by growing Gyromitra mycelium in conditions that result in differential production of gyromitrin and correlating gyromitrin production to gene expression. We are also comparing the genomes of Gyromitra species that do and do not produce gyromitrin. Finally, we aim to knock out putative gyromitrin biosynthesis genes to confirm that they are responsible for mycotoxin production. 

​Fungi produce an enormous diversity of powerful secondary metabolites (think penicillin, lovastatin, and cyclosporin, among many others), but the genetics and evolution of the vast majority are unknown. This research could expand our understanding of nitrogen-nitrogen secondary metabolite biosynthesis specifically and fungal chemodiversity in general, aiding in the discovery of novel chemicals. 

3. Evolution of gyromitrin

Once we identify the genes responsible for gyromitrin production, we can explore its evolutionary history. Which evolutionary processes gave rise to gyromitrin production in lorchel mushrooms? Given that gyromitrin has been detected in Gyromitra leucoxantha and the Gyromitra esculenta group but not any other species, horizontal gene transfer is likely a principal mechanism. Using whole genome sequences, we will compare gene trees to the phylogenomics species tree to determine how the gyromitrin genes evolved. Genome-level data will also clarify evolutionary relationships in the family, resulting in taxonomic modifications.

Taxonomy of Crust Fungi

Crust fungi (or corticioid fungi) typically do not evoke much excitement or command great respect. However, they are extremely diverse and ecologically important. This is in part due to the fact that crust fungi are a form group. They are defined not by shared ancestry but by having the same crusty two-dimensional form. In other words, wherever you look across the basidiomycetes, you find crusts. Crust fungi make up for their lack of macroscopic charisma with extraordinary microscopic diveristy, representing the entire spectrum of spores, hyphae, and sterile cells of the Agaricomycotina subphylum. While many crusts break down dead wood, some form mutualistic associations with trees. Indeed, in some forests, crust fungi are the dominant members of the ectomycorrhizal community. The bottom of sticks and decaying logs is a great location to find crusts, but you can also find them on leaves, under conifer duff, on bark, and even on the underside of rocks! I endeavor to describe new species​ of crust fungi and document North American species at my other website, crustfungi.com. In the future, I'd like to make this website dynamic so that crust enthusiasts across North America can upload profiles for their favorite species. If you are a web developer and want to work on a Wordpress version of this website so others can participate, please let me know!

Past Research

Metabarcoding of Arbuscular Mycorrhizal Fungi

For my Master's thesis, I characterized the communities of arbuscular mycorrhizal fungi associating with switchgrass, a perennial biofuel feedstock, using long-read, high-throughput PacBio metabarcoding. Read more at Applied and Environmental Microbiology. 

Taxonomy of the Anamorph Sphaerosporium lignatile

As part of the international Fungal Systematics and Evolution (FUSE) collaboration, we resolved the familial status of the previously unplaced fungus Sphaerosporium lignatile as Pyronemataceae (Pezizales), closely related to the eyelash cup fungus (Scutellinia​). Check it out here. 

DNA Barcoding of the 2018 Smith Foray Macrofungi

We DNA barcoded 63 mushrooms that were collected during the 2018 Smith Foray in Mazomanie, WI. Three species were first reports for the United States and 15 were new records for Wisconsin. The manuscript was published in The Great Lakes Botanist. 

Boston Harbor Islands Fungal Biodiveristy Survey

As my first experience in mycology, I worked with the nonprofit organization Boston Harbor Now, Harvard University, and the National Park Service in collecting and documenting fungi from the Boston Harbor Islands National Park. Our findings were published in Northeastern Naturalist.