CAREER: Cellular Mechanisms of Killer Toxin Resistance in Yeasts

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).

Fungal cells separate themselves from their environment by constructing a robust cell wall made of carbohydrates and proteins with an underlying membrane. This enables the compartmentalization of metabolic processes and protects fungal cells from external stressors, including commercial fungicides that are used extensively to control unwanted fungal growth.

Antifungal proteins produced by different species of fungi can attack the cell wall and membrane causing injury and the death of susceptible fungal cells. These antifungals have been cited as potentially being useful to control the growth of undesirable fungi. This research will explore the fundamental cellular mechanisms that are employed by fungi to resist intoxication by antifungal proteins.

Specifically, the project will test how mutations in genes used for cell wall and membrane construction and stability result in resistance to antifungal proteins. Antifungal proteins are produced by a significant proportion of fungi, especially by yeasts that are associated with insects, fruits, and fermentation (e.g. brewing and baking). The general familiarity of the public with yeasts will enable schoolchildren and patrons of the local farmer’s market to participate in the isolation of yeasts that produce novel antifungal proteins.

These outreach activities will be enhanced by the participation of undergraduate research students to enable the identification of novel antifungal proteins and their application to further investigate the function and organization of the fungal membrane and cell wall. Students from underrepresented groups at the University of Idaho will also be included in research activities.

The central goal of this approach is to increase retention of university students, enrollment in higher education of postsecondary and postbaccalaureate students, and to improve public STEM education.

The goal of this research is to discover the cellular mechanisms that are important for fungal resistance to antifungal “killer” toxins. This will uncover novel pathways that are important for cell surface function and resilience. The research hypotheses are that the Regulator of Ace2 and Cell Morphogenesis (RAM) signaling network plays an undescribed role in cell wall and membrane organization, and that the localization and diversity of the killer toxin receptor Kre1p is essential for intoxication by killer toxins.

These hypotheses were formulated based on preliminary data that has identified mutations in the RAM network that result in killer toxin resistance and the loss of membrane and cell wall integrity. To test these hypotheses, it will be determined how mutations in the RAM network that cause killer toxin resistance alter the networks organization, localization, and function relating to cytokinesis and cell polarity.

Specifically, the effect of these mutations on the localization of the killer toxin membrane receptor (Kre1p) will be tested. This approach will be complemented by an in-depth study of the effect of Kre1p diversity on killer toxin resistance and the immunity mechanisms of killer yeasts that prevent self-intoxication. The outcome of this research will be to confirm the novel role of the RAM network in cell surface organization.

This will be complemented by the investigation of the RAM network and Kre1p and their role in killer toxin resistance.

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.