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Characterization of the Brassica napus-fungal pathogen interaction Open Access

Descriptions

Other title
Subject/Keyword
Canola -- Diseases and pests
Fungal diseases of plants
Phytopathogenic microorganisms
Sclerotinia sclerotiorum
Plant-pathogen relationships
Type of item
Thesis
Degree grantor
University of Alberta
Author or creator
Yang, Bo
Supervisor and department
Dr. Nat Kav (Department of Agricultural, Food and Nutritional Science)
Examining committee member and department
Dr. Stephen Strelkov (Department of Agricultural, Food and Nutritional Science)
Dr. Michael Deyholos (Ddepartment of Biological Sciences)
Department
Department of Agricultural, Food, and Nutritional Science
Specialization

Date accepted
2009-05-27T20:40:06Z
Graduation date
2009-11
Degree
Doctor of Philosophy
Degree level
Doctoral
Abstract
Sclerotinia sclerotiorum is a devastating pathogen causing stem rot in Brassica napus (canola). Microarray analysis was performed to investigate pathogen-induced transcript profiling in B. napus responses to S. sclerotiorum. Several genes were identified, which included defensins, those encoding proteins involved in oxidative burst, the biosynthesis of jasmonic acid (JA), and several transcription factors (TFs), but not salicylic acid (SA)-related genes. To further characterize the roles of SA, JA and ethylene (ET) in the response of B. napus and Brassica carinata (tolerant species) to S. sclerotiorum, the expression of five genes known to respond to these phytohormones were investigated. We observed that S. sclerotiorum triggered JA/ET signaling in B. napus. Furthermore, the heterologous expression of 1-aminocyclopropane- 1-carboxylate (ACC) deaminase, which reduced ET levels, enhanced the susceptibility of B. napus to S. sclerotiorum. Our microarray analysis also revealed the importance of TFs in mediating responses of B. napus to S. sclerotiorum. To probe the involvement of one such TF family in B. napus, the WRKYs, public sequence databases were mined. Three groups of B. napus WRKYs were indentified from a phylogenetic tree and four selected ones were shown to localize to the nucleus using GFP fusions. Sclerotinia sclerotiorum and Alternaria brassicae (another necrotrophic pathogen affecting canola) and phytohormone-induced expression of representative WRKYs from each clade was also investigated using quantitative real-time PCR. In another aspect of our study, two recombinant single chain variable fragment (ScFvs) antibodies specific for a S. sclerotiorum endopoly-galacturonase (SSPG1d) were isolated and characterized. Our results indicated that these antibodies may have utility in the detection of this pathogen when used with other S. sclerotiorum-specific antibodies in a panel format assay. Transgenic Arabidopsis expressing the ScFvs were evaluated for tolerance to S. sclerotiorum and it was observed that the heterologous expression of the cDNAs encoding these ScFvs did not enhance the tolerance of Arabidopsis. However, additional research aimed at stabilization of the ScFvs and/or their localization must be conducted together with research into their usefulness in imparting tolerance in B. napus to this pathogen, since the observed effects in this species may be different from A. thaliana.
Language
English
DOI
doi:10.7939/R3Z10W
Rights
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
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