<i>Sclerotinia sclerotiorum</i> : phytotoxins and metabolism of phytoalexins
<i>Sclerotinia sclerotiorum </i>(Lib.) de Bary is a plant pathogenic fungus causing serious yield losses in a broad range of cultivated plants, excluding cereals. Most of the economically important brassicas such as canola, rapeseed, mustards, cabbages and others such as sunflower, peanu...
Main Author: | |
---|---|
Other Authors: | |
Format: | Others |
Language: | en |
Published: |
University of Saskatchewan
2008
|
Online Access: | http://library.usask.ca/theses/available/etd-07232008-134049/ |
id |
ndltd-USASK-oai-usask.ca-etd-07232008-134049 |
---|---|
record_format |
oai_dc |
spelling |
ndltd-USASK-oai-usask.ca-etd-07232008-1340492013-01-08T16:33:21Z <i>Sclerotinia sclerotiorum</i> : phytotoxins and metabolism of phytoalexins Ahiahonu, Pearson William Kwaku <i>Sclerotinia sclerotiorum </i>(Lib.) de Bary is a plant pathogenic fungus causing serious yield losses in a broad range of cultivated plants, excluding cereals. Most of the economically important brassicas such as canola, rapeseed, mustards, cabbages and others such as sunflower, peanut, bean, soybean, lettuce, and carrot are susceptible to this pathogen. No host specificity has been demonstrated in<i> S. sclerotiorum</i> and there is no specific resistance known in the host species. The main trust of this research project was to establish biotransformation pathways used by<i> S. sclerotiorum</i> to detoxify phytoalexins produced by host plants. As well, the potential production of phytotoxins and cytotoxic compounds by<i> S. sclerotiorum</i> was analyzed. The metabolite sclerin was isolated from cultures of <i>S. sclerotiorum</i> and its phytotoxicity to crucifers established for the first time. Fatty acids isolated from sclerotia of <i>S. sclerotiorum</i> of which oleic acid was a major component were found to be cytotoxic to the brine shrimp (<i>Artemia salina</i>).<p> Chemical defences, i.e. phytoalexins, were elicited and isolated from a resistant plant (<i>Erucastrum gallicum</i>, dog mustard): indole-3-acetonitrile, arvelexin, 1-methoxyspirobrassinin and erucalexin (new phytoalexin, a structural isomer of 1-methoxyspirobrassinin). As well, the biotransformations of the phytoalexins brassinin, produced by rapeseed, canola and brown mustard plants, camalexin, and 6-methoxycamalexin, produced by wild crucifers like<i> Arabidopsis thaliana, Capsella bursapastoris</i> and <i>Camelina sativa</i>, were investigated. It was established that <i>S. sclerotiorum</i> could efficiently metabolize these phytoalexins using a remarkable glucosylation reaction of their indole ring. Overall, results of these biotransformation studies followed by antifungal bioassays indicated that metabolism of brassinin, camalexin, and 6-methoxycamalexin were detoxification processes. Analogues of these phytoalexins were designed based on structures of the detoxification products to probe the specificity or otherwise of the enzyme(s) involved in the metabolism of the phytoalexins. All the analogues tested were metabolized by the fungus though at slower rates. 6-Fluorocamalexin, one of the analogues, significantly slowed down the metabolism of brassinin both in cell cultures and in enzymatic assays with cell homogenates. Partial purification (five fold) of the brassinin detoxifying enzyme (brassinin glucosyltransferase) of <i>S.sclerotiorum</i> was achieved. Reid, R. Stephen Palmer, David Lin, Yen-Hen Hultin, Philip Ward, Dale E. University of Saskatchewan 2008-08-11 text application/pdf http://library.usask.ca/theses/available/etd-07232008-134049/ http://library.usask.ca/theses/available/etd-07232008-134049/ en unrestricted I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Saskatchewan or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
collection |
NDLTD |
language |
en |
format |
Others
|
sources |
NDLTD |
description |
<i>Sclerotinia sclerotiorum </i>(Lib.) de Bary is a plant pathogenic fungus causing serious
yield losses in a broad range of cultivated plants, excluding cereals. Most of the
economically important brassicas such as canola, rapeseed, mustards, cabbages and others
such as sunflower, peanut, bean, soybean, lettuce, and carrot are susceptible to this
pathogen. No host specificity has been demonstrated in<i> S. sclerotiorum</i> and there is no specific resistance known in the host species. The main trust of this research project was to establish biotransformation pathways used by<i> S. sclerotiorum</i> to detoxify phytoalexins
produced by host plants. As well, the potential production of phytotoxins and cytotoxic
compounds by<i> S. sclerotiorum</i> was analyzed. The metabolite sclerin was isolated from cultures of <i>S. sclerotiorum</i> and its phytotoxicity to crucifers established for the first time.
Fatty acids isolated from sclerotia of <i>S. sclerotiorum</i> of which oleic acid was a major
component were found to be cytotoxic to the brine shrimp (<i>Artemia salina</i>).<p>
Chemical defences, i.e. phytoalexins, were elicited and isolated from a resistant
plant (<i>Erucastrum gallicum</i>, dog mustard): indole-3-acetonitrile, arvelexin,
1-methoxyspirobrassinin and erucalexin (new phytoalexin, a structural isomer of
1-methoxyspirobrassinin). As well, the biotransformations of the phytoalexins brassinin,
produced by rapeseed, canola and brown mustard plants, camalexin, and 6-methoxycamalexin,
produced by wild crucifers like<i> Arabidopsis thaliana, Capsella bursapastoris</i>
and <i>Camelina sativa</i>, were investigated. It was established that <i>S. sclerotiorum</i>
could efficiently metabolize these phytoalexins using a remarkable glucosylation reaction
of their indole ring. Overall, results of these biotransformation studies followed by antifungal bioassays indicated that metabolism of brassinin, camalexin, and 6-methoxycamalexin were detoxification processes. Analogues of these phytoalexins were designed based on structures of the detoxification products to probe the specificity or otherwise of the enzyme(s) involved in the metabolism of the phytoalexins. All the analogues tested were metabolized by the fungus though at slower rates. 6-Fluorocamalexin,
one of the analogues, significantly slowed down the metabolism of brassinin both in cell cultures and in enzymatic assays with cell homogenates. Partial purification (five fold) of the brassinin detoxifying enzyme (brassinin glucosyltransferase)
of <i>S.sclerotiorum</i> was achieved. |
author2 |
Reid, R. Stephen |
author_facet |
Reid, R. Stephen Ahiahonu, Pearson William Kwaku |
author |
Ahiahonu, Pearson William Kwaku |
spellingShingle |
Ahiahonu, Pearson William Kwaku <i>Sclerotinia sclerotiorum</i> : phytotoxins and metabolism of phytoalexins |
author_sort |
Ahiahonu, Pearson William Kwaku |
title |
<i>Sclerotinia sclerotiorum</i> : phytotoxins and metabolism of phytoalexins |
title_short |
<i>Sclerotinia sclerotiorum</i> : phytotoxins and metabolism of phytoalexins |
title_full |
<i>Sclerotinia sclerotiorum</i> : phytotoxins and metabolism of phytoalexins |
title_fullStr |
<i>Sclerotinia sclerotiorum</i> : phytotoxins and metabolism of phytoalexins |
title_full_unstemmed |
<i>Sclerotinia sclerotiorum</i> : phytotoxins and metabolism of phytoalexins |
title_sort |
<i>sclerotinia sclerotiorum</i> : phytotoxins and metabolism of phytoalexins |
publisher |
University of Saskatchewan |
publishDate |
2008 |
url |
http://library.usask.ca/theses/available/etd-07232008-134049/ |
work_keys_str_mv |
AT ahiahonupearsonwilliamkwaku isclerotiniasclerotiorumiphytotoxinsandmetabolismofphytoalexins |
_version_ |
1716532196370546688 |