Dissertation/Thesis Abstract

The Role of Ubiquitination in the Innate Immune System in Arabidopsis
by Guo, Tingwei, Ph.D., The University of Alabama, 2018, 101; 10815633
Abstract (Summary)

My research using the model plant Arabidopsis thaliana is focused on unraveling the signal transduction pathways involved in elicitor-mediated plant defense, particularly defense pathways involved in resistance to fungal pathogens. I have isolated a group of related genes, the ATL family, which appear to play a direct role in defense against fungal pathogens. Previous research has shown that ATL proteins can be induced by chitin and they are involved in basal resistance to the fungal pathogens.

ATL9, an Arabidopsis RING zinc finger protein, is an E3 ubiquitin ligase that can be induced by chitin and is involved in basal resistance to the fungal pathogen, Golovinomyces cichoracearum (G. cichoracearum). In order to understand the expression and regulation of ATL9, I studied the expression pattern of ATL9 and the functions of its different protein domains. Using a pATL9: GUS transgenic Arabidopsis line I found that ATL9 is expressed in different tissues in Arabidopsis at various developmental stages and that GUS activity was induced rapidly upon wounding. Previous research in our lab also showed that ATL9 is a short-lived protein within plant cells and it is degraded via the ubiquitin-proteasome pathway. Protein prediction software indicated that ATL9 contains two transmembrane domains (TM), a RING zinc-finger domain, and a PEST domain. Data from confocal microscopy and western analysis indicate that both the PEST domain and the RING domain have effects on ATL9 degradation. To study the importance of these domains in ATL9's function, I constructed a series of deletion mutants and generated transgenic Arabidopsis plants. As expected, transgenic Arabidopsis containing the deletion constructs showed that both the RING domain and the TM domains are important to its resistance phenotype against G. cichoracearum. Interestingly, the PEST domain was also shown to be significant for the resistance to fungal pathogens. Additionally, I discovered that ATL9 can bind the defense related proteins FBS1, PCC1, and PDF1.2 directly and degrade them via the proteasome. Finally, I propose a hypothesized mechanism is proposed describing the function of ATL9 and its possible interaction with other proteins in enhancing the plant defense response.

Indexing (document details)
Advisor: Ramonell, Katrina M.
Commitee: Dawe, Angus, O'Donnell, Janis M., Powell, Martha J., Reed, Laura
School: The University of Alabama
Department: Biological Sciences
School Location: United States -- Alabama
Source: DAI-B 80/02(E), Dissertation Abstracts International
Subjects: Biology, Molecular biology, Cellular biology
Keywords: Chitin, Plant defense, Plant innate immunity, Plant pathogen ineraction, Protein-protein interaction, Ubiquitination
Publication Number: 10815633
ISBN: 978-0-438-44214-6
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