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Pengfei Bai OSU PhD dissertation.pdf (5.08 MB)

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Dissecting the Layered Rice Innate Immunity at the Molecular, Genetic, and Metabolomic Levels

Bai, Pengfei
http://orcid.org/0000-0002-2281-2881
http://rave.ohiolink.edu/etdc/view?acc_num=osu1525780095074052

Abstract Details

2018, Doctor of Philosophy, Ohio State University, Plant Pathology.
Growing resistant varieties has been recognized as a cost-effective approach to plant disease management. However, the benefit of this application has been compromised by the ineffectiveness of previously identified resistance (R) genes to the new emerging races of plant pathogens. By using the rice-Magnaporthe oryzae (M. oryzae) pathosystem as a model, the research aimed to elucidate the regulatory mechanisms of plant immunity at the molecular, genetic, and metabolomic levels. Research topics include effector-triggered recognition, R gene-mediated resistance, receptor-like kinase (RLK)-regulated immunity and programmed cell death (PCD), and pathogen induced-metabolomic changes. The M. oryzae avirulence (Avr) effector AvrPiz-t targets the host ubiquitin-proteasome system to manipulate plant defense, but the process by which AvrPiz-t activates Piz-t-mediated resistance is not fully understood. We generated the lysine-free mutant LF-AvrPiz-t and found that lysine residues in AvrPiz-t are critical for its protein stability, avirulence and virulence function during M. oryzae infection. However, the specific recognition between Piz-t and AvrPiz-t seems more complicated than a receptor-ligand interaction. To explore Piz-t-mediated resistance, we identified a total of twenty-eight Piz-t associated proteins (PAZs) from HA-tagged Piz-t transgenic rice by using immunoaffinity chromatography. Six PAZs were confirmed for their interaction with Piz-t by a semi-GST pulldown assay. PAZ14, a short-chain dehydrogenase, acts as a positive regulator of rice basal defense. Silencing PAZ14 in the Piz-t background makes rice plants more susceptible to the M. oryzae isolate RB22-AvrPiz-t, suggesting the involvement of PAZ14 in Piz-t-mediated resistance. RLKs play a fundamental role in the hierarchical regulation of plant immunity. We identified two RLCK VII subfamily proteins OsRLCK118 and OsRLCK176 as a positive regulator of rice blast resistance. The protein-protein interaction assays demonstrated that both OsRLCK118 and OsRLCK176 interact with the NADPH oxidase OsRBOHB (for Respiratory Burst Oxidase Homolog B), and an in vitro phosphorylation assay showed that OsRLCK118 phosphorylates OsRBOHB for the potential regulation of rice reactive oxygen species (ROS) production. We also demonstrated that OsRLCK118 and OsRLCK176 interact with a monocot-specific RLK, SDS2, which is a positive regulator of rice immunity and PCD. The SDS2-dependent phosphorylation of OsRLCK118 upon the chitin treatment connects the extracellular perception of pathogen-associated molecular patterns (PAMPs) by an unknown receptor to the intracellular activation of ROS production. Suppression of SDS2 overexpression-caused immunity and PCD by the OsRLCK118 mutation further confirmed the SDS2-OsRLCK118-RBOHB-based phosphor-signaling pathway in the regulation of rice immunity and PCD. To understand the chemical basis of plant disease resistance, we profiled the metabolomic changes of both resistant and susceptible rice varieties to M. oryzae infection and found as-yet-unidentified “clusters” of metabolite peaks. The number of differential metabolic peaks from the comparison of the infected vs. non-infected, resistant vs. susceptible, and different timepoints provided a general picture of rice metabolic changes during M. oryzae infection. Overall, the research presented here enriches our understanding of multi-layered plant immunity, while the novel defense-related genes and metabolites identified will provide options for selecting and engineering disease resistant rice plants.
Guo-Liang Wang (Advisor)
Feng Qu (Committee Member)
David Mackey (Committee Member)
Joshua Blakeslee, J. (Committee Member)
Margaret Redinbaugh, G. (Committee Member)
206 p.
Plant Pathology
Rice immunity; ETI; PTI; Receptor-like kinase; pathogen induced-metabolomic changes

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Citations

  • Bai, P. (2018). Dissecting the Layered Rice Innate Immunity at the Molecular, Genetic, and Metabolomic Levels [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1525780095074052

    APA Style (7th edition)

  • Bai, Pengfei. Dissecting the Layered Rice Innate Immunity at the Molecular, Genetic, and Metabolomic Levels . 2018. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1525780095074052.

    MLA Style (8th edition)

  • Bai, Pengfei. "Dissecting the Layered Rice Innate Immunity at the Molecular, Genetic, and Metabolomic Levels ." Doctoral dissertation, Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1525780095074052

    Chicago Manual of Style (17th edition)

osu1525780095074052
401
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This open access ETD is published by The Ohio State University and OhioLINK.