The chemistry of host-parasite fidelity

• Applicant: Dr. Aileen Berasategui
• Subject Area: Evolution, Anthropology ; Evolution and Systematics of Plants and Fungi ; Microbial Ecology and Applied Microbiology
• Term: from 2019 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 419004542

Chemical signals can drastically impact how species interact. While influential in dictating reproductive courtships and predator-prey dynamics, little is known concerning the chemical ecology of host-parasite interactions. Using the dynamic and well-studied fungus-farming ants as a model, I aim to better understand the chemical underpinnings driving the metabolic intimacy of a co-evolved host-parasite system. Fungus-farming ants are a charismatic group of monophyletic insects comprising more than 230 species, and cultivate fungi as their primary food source. Each ant species grows a narrow range of fungal cultivars. These cultivars are hosts to morphologically and phylogenetically diverse species of fungal parasites in the genus Escovopsis. Horizontally-transmitted Escovopsis parasites attack and consume the fungal cultivar, which can lead to rapid colony decline. Prior studies reveal that Escovopsis are able to respond to undescribed host chemical cues, and that their host cultivars can defend against Escovopsis. These properties lead to each Escovopsis strain being able to utilize only a narrow range of cultivar hosts. Given the potential role that natural products can play in parasite specificity, I aim to explore the diversity of mechanisms leading to specialization of Escovopsis fungal parasites on their cultivar hosts by (1) elucidating the chemicals governing parasite attraction and host defense, and (2) investigating the diversity of parasite-produced toxins involved in the early stages of cultivar invasion.Exploring the chemical dimension of parasite specialization using the cultivar-Escovopsis system represents a unique model since: (1) both host and parasite are cultivable (and are available at Emory University), (2) specific inoculation methods exist in order to assess virulence in vitro through precise bioassays testing patterns of resistance and infectivity for large-scale evaluation, and (3) recently developed methods now allow for the coupling of molecular and metabolomic techniques in fungal systems for large-scale discovery of natural products.

• DFG Programme: Research Fellowships
• International Connection: USA
• Host: Professorin Dr. Nicole Gerardo