EAGER: Mysterious Lack of Intracellular Fungal Symbionts in Insects

Fungi and bacteria often form partnerships with insects that help both organisms survive. These partnerships, called symbioses, are common and well-studied in bacteria, but surprisingly rare in fungi—especially when it comes to fungi that live inside insect cells. This project seeks to understand why these fungal-insect partnerships are so unusual. By studying the relationship between Deathwatch beetles and their fungal partners, researchers aim to uncover how and why these associations evolve and what prevents fungi from forming long-term beneficial partnerships like bacteria do. This knowledge could help scientists better understand how some fungi switch between being helpful partners to harmful pathogens, which has implications for health, agriculture, and biodiversity. In addition, the project will train graduate and undergraduate students and engage the local community through educational events in New Mexico, encouraging a deeper appreciation of the microbial world that affects everyday life. The research will investigate two lineages of intracellular fungal symbionts—Symbiotaphrina and Nakazawaea—associated with Deathwatch beetles. The project aims to uncover genomic and evolutionary factors that may influence the rarity of intracellular fungal mutualisms, particularly in comparison to more commonly studied bacterial systems. By examining patterns of genome structure and stability, the study seeks to explore how different evolutionary pressures may shape the long-term potential for symbiotic relationships in fungi. The study will pursue three main aims: (1) reconstruct the co-evolutionary history of Deathwatch beetles and their fungal symbionts using ultraconserved element (UCE) sequencing for beetles and ITS sequencing for fungi; (2) compare genome architecture, including synteny, pseudogene content, and mobile element activity, between intracellular fungi and closely related free-living species; and (3) assess phenotypic traits such as nutrient usage, heat tolerance, and cell morphology in lab-grown fungal strains. These analyses will provide foundational insights into the evolution and stability of fungal-insect mutualisms and the broader principles that govern symbiotic relationships. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.