Date of Graduation

12-2023

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Agricultural, Food and Life Sciences (PhD)

Degree Level

Graduate

Department

Entomology and Plant Pathology

Advisor/Mentor

Egan, Martin J.

Committee Member

Korth, Kenneth L.

Second Committee Member

Wang, Yong

Third Committee Member

Lewis, Jeffrey A.

Keywords

appressorium; cytokeleton; Fluorescence; Magnaporthe oryzae; Rice Blast

Abstract

Understanding the intricate processes underlying fungal infection-related development is crucial for combating plant pathogens. In this study, we investigate the coordination of morphogenetic transitions during plant infection by Magnaporthe oryzae, the blast fungus. We focus on three key aspects: protein quality control, cytoplasmic microtubule organization, and cell-end marker proteins. M. oryzae forms a specialized infection cell known as an appressorium. The proper formation of this cell is crucial for the pathogen to infect a susceptible host. First, we investigate protein quality control mechanisms during infection-related development. Our findings demonstrate that aggregated proteins are sequestered into quality control compartments within conidia but not in terminally differentiated infection cells, highlighting cell type-dependent spatial protein quality control. Impaired aggregate resolution incurs a short-term developmental penalty but does not significantly affect appressorium function. Surprisingly, we uncover the requirement of autophagy machinery for normal aggregate formation and compartmentalization. Next, we explore the organization and dynamics of cytoplasmic microtubules, essential for motor-driven organelle motility. Through live-cell imaging, we discover that microtubules are nucleated at septa, not nuclear spindle pole bodies, in the blast conidium. We also reveal insights into microtubule remodeling during nuclear division and inheritance. Furthermore, we provide a comprehensive understanding of the architecture and subcellular organization of the specialized blast appressorium. Finally, we elucidate the behavior of Tea1, a cell-end marker protein, and its role in appressorium differentiation and vegetative growth. Tea1's localization transitions from the germ tube's equatorial plane to discrete clusters around the appressorium's outer edge, spatially controlling F-actin nucleation and contractile ring emergence. Furthermore, Tea1's involvement in hyphal septation suggests a role in branch emergence. Loss of Tea4 leads to abnormal Tea1 localization and impaired growth directionality, emphasizing the importance of Tea1-Tea4 interplay. Overall, this study offers valuable insights into the coordination of morphogenetic transitions, microtubule organization, and protein quality control in Magnaporthe oryzae. The findings shed light on the complex interplay between these processes during infection-related development, providing a foundation for understanding fungal pathogenesis and potential targets for disease control strategies.

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