The emergence of new infectious diseases or modification of existing diseases refractive to treatment, or with expanded host range, poses serious threats to human survival. This project will explore genetic and molecular underpinnings of such disease emergence, and may allow better prediction of emerging infectious diseases through host shifts. The fungi, members of the Microbotryum violaceum fungal species complex, that infect a large diversity of wildflower species in the Carnation family (Pinks), provide a unique model compared with organisms that cause disease on more genetically homogeneous agricultural plants. Since shifts of these host-specific fungi to new wildflower species has been observed in nature, understanding the range and limits of such shifts, as well as the genes and proteins involved could provide a unique approach for dealing with ever-increasing diseases that either directly or indirectly affect human health and survival (e.g., by threatening food supply). In the process of investigating such fundamentally and practically important scientific questions, this project will also provide training to a range of students and professional trainees (from undergraduate to graduate student to Postdoctoral), in areas of comparative population genomics and proteomics, and in technical training in state-of-the-art methods used in molecular biological and biotechnological investigations. Concerted recruitment efforts established by the PI target candidates from traditionally under-represented groups in the region of Kentucky and the Southeastern US (specifically, African-Americans, Latinx, women, Appalachians) that enhances their pursuit of an advanced degree. Moreover, a “bridge year” will be established to support recruits as mentors for subsequent minority students recruited.

The Microbotryum violaceum complex of fungal plant pathogens is a useful model of emerging infectious diseases through host shifts. As pathogens on genetically more diverse host plant populations, the M. violaceum complex provides an important alternative model to pathogens on agricultural generally homogenous hosts. Pathogenic fungi often secrete effector proteins to manipulate their hosts and these may be an important aspect of host specialization. In Aim 1, populations of Microbotryum on Dianthus host species will be compared to test the hypothesis that fungal small secreted proteins (SSPs) play important roles in localized host adaptation/specificity. Via comparative genomics, we already identified possible Microbotryum SSP effectors across 3 Microbotryum species. Here, comparisons will be added, of “generalist” Microbotryum species on Dianthus hosts with a “specialist” species, limited to one Dianthus host species, to test predictions of local adaptations, reflected in effector function, within the same Microbotryum species. Aim 2 will validate possible effectors in plant hosts. Expression levels in each fungus, modified by over-expression of specific candidate effector genes via “mix and match” experiments, will assess ability of effectors from one fungal species to expand the host range of another species. CRISPR/Cas9 will be used to delete effectors in fungi and test such mutants in plants. Candidate effector genes in host plants, absent the fungus, will test the hypothesis that the candidate effector is responsible for plant pathology, possibly by modifying host development; such experiments will also provide localization in planta, co-localization studies of effectors and predicted host targets, and Co-IP.

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.

National Science Foundation (NSF)
Division of Integrative Organismal Systems (IOS)
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Michael Mishkind
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University of Louisville Research Foundation Inc
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