I am a mycologist and evolutionary biologist interested in the evolution and maintenance of sexual reproduction, genomic organization, and how symbiotic interactions like mutualism and parasitism affect genetic variation. I am particularly interested in studying these phenomena in basidiomycete fungi, which spend a long portion of their life as dikaryons, where each cell contains two (often) genetically distinct haploid nuclei. This life history trait allows us to ask unique questions about cell idenity, genomic conflict, and ploidy such as:

• Are dikaryotic cells equivalent to diploid cells?
• How do nuclei sense their ploidy and what signals or properties lead to karyogamy?
• How is transcription coordinated between nuclei in a cell? Are some nuclei silent?
• What are the evolutionary pressures that drive the separation of plasmogamy (cell fusion) and karyogamy (nuclear fusion)?

The lifecycle of Schizophyllum commune, showing a prolonged dikaryotic stage (4). The nuclei only fuse in the basidospore producing cells in the mushroom (7). A and B refer to mating types, which control the ability of monokaryons (2) to form dikaryons with each other. Illustration by Sarah Friedrich, from Young and Pringle (2024).

Characterizing the genomic organization of ant-associated Leucoagaricus spp.

In contrast to many basidiomycetes, some ant-associated Leucoagaricus spp. are polykaryotic, with between 4-30 nuclei per cell instead of the usual two. Using flow cytometry and whole genome sequencing, I am working on characterizing both how many distinct genome types (equivalent to ploidy) are present in individaul strains, and how genome types are distributed between different nuclei.

Image of a multinucleate Leucoagaricus cell. Nuclei are stained in blue and septa is indicated with arrow

Characterizing the mating-type loci in Escovopsis

Escovopsis is a fungal parasite of Leucoagaricus and likely followed Leucoagaricus into the fungus-growing ant symbiosis. Previous genomic analyses have suggested that Escovopsis has lost it's mating-type loci, which are the master regulators of sexual reproduction in fungi. I am working on understanding the evolution, and potential loss, of the mating-type loci in Escovopsis. Escovopsis overgrowing a fungus garden composed of Leucoagaricus tissue

Rethinking terminology for fungal sex

Mycologists have imported animal sexual categories, like male and female (and even the concept of sex categories themselves), into fungi. However, the use of this terminology when talking about fungal sex is not appropriate or accurate. In fact, fungal sexual reproduction is incredibly diverse, and studying it can help all biologists better understand the evolution of sex. I am working on critiquing and rethinking how we talk about fungal sex in order to better represent fungal biology, and avoid using harmful and loaded language.