Food security is a grand challenge facing humanity in the face of climate change and population growth; yet, on a global scale up to 15% of crops are lost to pathogens each year. Protecting crops from pathogens is a critical, ongoing global initiative. Many agriculturally important diseases are caused by powdery mildew and rust fungi, and fungus-like oomycete pathogens. One common feature of these evolutionarily distinct pathogens is that they develop similar feeding structures called haustoria to invade plants and extract nutrients from host cells. Despite tremendous progress towards understanding the molecular mechanisms of plant resistance against pathogens, how the host defense is executed in the plant-haustorial interface is still poorly characterized. The research aims to identify and functionally characterize novel molecular players at the host-pathogen interface termed the extrahaustorial membrane using a model pathosystem and state-of-the-art genetics and biochemistry tools. New findings from this project will not only lead to a better understanding of the molecular composition of the host-pathogen interface but also help design novel strategies to fight against haustorium-forming pathogens and reduce crop losses, thereby contributing to sustainable agriculture.

Haustorium-forming pathogens such as powdery mildew fungi develop a feeding structure termed the haustorium in host tissues to secrete effector proteins capable of suppressing the host immune response and extracting nutrients from the host cell. The haustorium is physically separated from the host cell by a host-derived interfacial membrane named the extrahaustorial membrane (EHM). The EHM is believed to be the most critical host-pathogen battleground, where the host defense is mounted to constrain the haustorium, and the pathogen deploys effectors to subvert host immunity and extracts nutrients from the host. However, despite the importance of the EHM, its molecular components and the mechanisms associated with host defense or pathogenesis are poorly characterized. The long term goal of this project is to understand the protein composition of the EHM and the mechanisms of plant-haustorium interactions at this host-pathogen interface. Using the Arabidopsis-powdery mildew interaction as a model pathosystem and RPW8.2 (a broad-spectrum resistance protein) as the first and best EHM-specific resident protein, a collaborative team will (i) identify and characterize proteins interacting with RPW8.2 at the EHM and additional EHM-resident proteins via proximity-based labeling coupled with enrichment/purification of haustorial complexes followed by mass spectrometry; (ii) resolve the protein structure of RPW8.2 and understand how EHM-oriented vesicle transport of RPW8.2 is regulated by a candidate SNARE complex at the Trans-Golgi Network; and (iii) identify host susceptibility factors, such as sugar transporters, which may be recruited to the EHM by powdery mildew fungi for nutrient acquisition through both genetic and cell biological approaches.

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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Brad Day
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University of Maryland College Park
College Park
United States
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