Plants respond to and defend themselves against a wide range of disease-causing
microbes. In order to do so, massive reprogramming of cellular protein expression
patterns, which underpin various defense pathways, must occur. A family of basic
leucine zipper transcription factors, called TGA factors, has been implicated in
mediating this response. The TGA factors themselves are subject to complex regulation;
of note, TGA1 and TGA4 are regulated via a reduction of conserved cysteines after
treatment with the phenolic signaling molecular salicylic acid, which accumulates
following pathogen challenge. Previous studies indicate that TGA factors physically
interact in the yeast two-hybrid system with the plant-specific CC-type of glutaredoxin
(Grx)-like proteins. Grx are a family of oxidoreductases that are important for
maintaining the cellular redox status and often are required to modulate protein activity.
The goal of this study was to ascertain the role of these Grx-like proteins in regulating
TGA1 redox state. To this end, the expression patterns of several Grx genes were
analyzed.<p>
Quantitative-reverse-transcriptase PCR (q-RT-PCR) experiments indicated that
TGA1 and TGA4 may be involved in down-regulating levels Grx-like gene transcripts
after exposure to pathogens or salicylic acid (SA). Furthermore, qRT-PCR experiments
also indicated that expression of some Grx-like genes is induced by SA, jasmonic acid
(JA), and <i>Pseudomonas syringae</i>. Overexpression of the Grx-like protein, CXXC9, in
<i>Arabidopsis thaliana</i> revealed that it is a regulatory factor in the cross-talk between
vi
theSA/JA pathways as it is able to suppress expression of PDF1.2, a marker for the JA
defense pathway, as determined by qRT-PCR. The รข-hydroxy ethyl disulfide (HED)
assay was utilized to determine if the CC-type of Grx-like proteins have oxidoreductase
activity <i>in vitro</i>. These studies revealed that that the Grx-like proteins do not exhibit
oxidoreductase activity in this assay.
| Identifer | oai:union.ndltd.org:USASK/oai:usask.ca:etd-06202009-170645 |
| Date | 07 July 2009 |
| Creators | Hahn, Kristen Rae |
| Contributors | Fobert, Pierre |
| Publisher | University of Saskatchewan |
| Source Sets | University of Saskatchewan Library |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://library.usask.ca/theses/available/etd-06202009-170645/ |
| Rights | 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. |
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