Molecular mechanisms integrating fungal growth with plant innate immunity suppression

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By addressing the fundamental question "How do fungal cells thrive in plant cells?" this project aims to resolve substantial issues in plant pathology regarding what molecular mechanisms integrate fungal metabolism and growth in host cells with sustained plant innate immunity suppression. The project involves forward and reverse genetics, genome-wide proteomic and metabolic approaches, and live-cell imaging to understand how the growth and metabolism of rice blast fungus in host rice cells is facilitated and linked to host immune suppression. This could lead to the development of novel crop protection strategies targeting molecular pathways that are critical for the growth of the fungus but are not required for the normal function of the host cell, and could shed new light on both the basic principles of cell growth, and on the nature and regulation of host-microbe interfaces. The educational objectives will expand scientific education by stimulating undergraduates' science learning, preparing graduate students for scientific life beyond the university, and inspiring scientific interest in underrepresented high school students.In order to cause plant disease, and in common with other plant-associated microbes, the devastating rice blast fungus Magnaporthe oryzae initially forms intimate associations with living rice cells and grows for the first few days of infection as a symptomless biotroph, elaborating invasive hyphae (IH) wrapped in plant-derived membranes, acquiring nutrients and evading rice innate immune responses as it spreads cell-to-cell. After 3-5 days of infection, M. oryzae undergoes a lifestyle transition to necrotrophy, resulting in disease symptom development, host cell death and sporulation from leaf lesions. How M. oryzae controls the development of IH during the biotrophic growth phase while simultaneously evading or suppressing host innate immunity, and what triggers the transition to necrotrophy following the extended biotrophic growth phase, is almost entirely unknown at the molecular level. This project seeks to address these knowledge gaps by generating and characterizing mutants of M. oryzae that are unable to colonize host plant cells. This is expected to uncover novel cellular, biochemical, and genetic mechanisms governing rice infection. Results from the proposed work could point to novel sources of disease resistance, shed light on fundamental concepts of plant host-microbe interactions, and indicate how beneficial plant-fungal interactions might be promoted while those detrimental to crop health are diminished. The work will foster the molecular training of postdoctoral, graduate and undergraduate students from diverse backgrounds through active participation in tackling the real-world problem of rice blast disease.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.