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Permanent link (DOI): https://doi.org/10.7939/R3M42K

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Studies on the Role and Mechanism of Action of Ptr ToxB from Pyrenophora tritici-repentis Open Access

Descriptions

Other title
Subject/Keyword
Effector
Host specific toxin
Ptr ToxB
Type of item
Thesis
Degree grantor
University of Alberta
Author or creator
Kim, Yong Min
Supervisor and department
Strelkov, Stephen (Agricultural, Food, and Nutritional Science)
Examining committee member and department
Kelly Turkington (AFNS/AAFC, Lacombe)
Michael Deyholos (Biological Sciences)
Nat Kav (AFNS)
Sheau-Fang Hwang (AFNS/AAFC, Edmonton)
Peter Solomon (Australian National University)
Department
Department of Agricultural, Food, and Nutritional Science
Specialization
Plant Science
Date accepted
2012-09-17T15:33:32Z
Graduation date
2012-09
Degree
Doctor of Philosophy
Degree level
Doctoral
Abstract
Tan spot is an important foliar disease of wheat caused by Pyrenophora tritici-repentis. This fungus produces Ptr ToxB, a host-specific toxin that induces chlorosis on sensitive host genotypes. An assessment of the effects of Ptr ToxB in a toxin-sensitive wheat line revealed that photosynthesis, as measured by infra-red gas analysis, declined significantly prior to the development of chlorosis. This decline was accompanied by changes in the leaf proteome, with 102 protein spots found to have altered intensities by 2-dimensional gel electrophoresis 12-36 h after toxin treatment. Forty-seven of these spots were identified by tandem mass spectrometry and included proteins involved in the light reactions of photosynthesis, the Calvin cycle, and the stress/defense response. These results suggest that Ptr ToxB disrupts photosynthesis in sensitive wheat, leading to oxidative stress and chlorophyll photooxidation. In another study, the ToxB gene encoding Ptr ToxB was transformed into a Ptr ToxB-non-producing isolate of P. tritici-repentis. The transformants induced chlorosis in a host-specific manner and caused significantly increased disease, with symptom severity correlated with the amount of Ptr ToxB produced. These findings indicate that the acquisition of toxin-producing ability is a sufficient condition for pathogenicity in P. tritici-repentis, and that Ptr ToxB confers virulence in a dosage-dependent manner. In a final study to explore the possible role(s) of ToxB homologs found in other ascomycetes, Pyrenophora teres, which causes net blotch of barley, was transformed with ToxB. Production of Ptr ToxB by P. teres increased virulence on net blotch-resistant and susceptible barley cultivars. However, while the transformants exhibited an altered infection phenotype on toxin-sensitive wheat, they did not cause the typical chlorosis associated with tan spot. This suggests that while ToxB homologs may play a role in the pathogenicity of this fungus, production of Ptr ToxB is on its own not sufficient for P. teres virulence on wheat. Collectively, these studies improved understanding of the role of Ptr ToxB in tan spot development and fungal virulence. An enhanced knowledge of tan spot and related pathosystems will facilitate rational strategies for disease management.
Language
English
DOI
doi:10.7939/R3M42K
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.
Citation for previous publication
Strelkov, S.E. and Lamari, L. (2003) Host-parasite interactions in tan spot Pyrenophora tritici-repentis of wheat. Can. J. Plant Pathol. 25, 339–349.Lamari, L. and Strelkov, S.E. (2010) The wheat/Pyrenophora tritici-repentis interaction: progress towards an understanding of tan spot disease. Can. J. Plant Pathol. 32, 4–10.

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