CAREER: Dissecting the Molecular Regulation of Septin-Mediated Plant Invasion by the Blast Fungus Magnaporthe Oryzae

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117- 2) The fungus Magnaporthe oryzae causes a highly destructive disease of cultivated rice and wheat, called blast, which poses an ongoing threat to food security around the world. In the field, blast is combatted using a limited range of fungicides, and the emergence of resistance to these chemistries is a looming threat. Thus, there is an urgent need to develop new strategies to control blast, but this demands a more complete mechanistic understanding of M. oryzae infection biology. To infect plants, M. oryzae produces a specialized pressure-generating infection cell, called an appressorium, which it uses to break inside of leaves. This research focuses on gaining a better understanding of how these infection cells are built and how they work, and therefore the outcomes may help to safeguard global food security and enhance agricultural productivity. The proposed activities will provide improved training and education in bioimaging for the study of plants, microbes and their interactions, and will provide enhanced opportunities for low-income, and first-generation high school students to gain hands-on research experience in cutting-edge fungal cell biology, therein promoting their participation in higher-education and science. Communication of these research outcomes at local events will provide enhanced opportunities for public engagement, leading to increased scientific literacy and awareness and greater trust in science and scientists. Appressorium-mediated plant invasion by M. oryzae requires the regulated assembly of a toroidal ring structure, composed of a class of cytoskeletal filament-forming GTP-binding proteins called septins, within its base. How this infection-specific septin ring forms in the right place, and at the right time, within the developing appressorium to enable plant invasion, remains largely mysterious. Indeed, understanding how septins are assembled and dynamically remodeled into different functional architectures in diverse cell types is a current frontier in the field. Critically, improved mechanistic understanding of septin ring assembly and function in M. oryzae may inform the development of new fungicides to control blast, and other fungal crop diseases, especially given that plants do not contain septins. The goals of this project are to gain new insight into the molecular mechanisms by which incipient septin disc-like structures form in the base of appressoria and are remodeled into rings, and how these cortical structures organize the penetration interface for plant invasion. This project combines the use of time-resolved proximity proteomics, live cell imaging, and reverse genetics to functionally map the septin-organized appressorium basal cortex and penetration interface and employs a novel fluorescence microscopy-based genome-wide chemical mutagenesis screen to identify novel regulators of septin ring assembly. 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.