The aim of this study was to investigate the early events following the infection of wheat
with leaf rust. An attempt was made to identify and characterize genes putatively involved
in these early events. More specifically, the aim was to obtain genes whose role in infected
plants could be linked to the resistance locus within the resistant plant.
DDRTâPCR was used to isolate differentially expressed genes from the resistant
Thatcher+Lr34 plants during the first 15 h after infection. Four cDNA fragments were cloned
and sequenced. The first clone coded for a monosaccharide transporter, while the second
clone encoded a cell wall invertase. Both these clones formed part of a different study to
postulate a role for these proteins during infection.
The third cDNA clone, coded for a putative heat shock protein. Heat shock proteins are
molecular chaperones and are normally involved in ensuring cellular homeostasis by
preventing the aggregation of denatured proteins and assisting in the folding and transport
of new and denatured proteins. The fourth clone encoded an indoleâ3âglycerol phosphate
lyase.
The expression of the putative heat shock protein increased 86 fold within 9 h.p.i in infected
resistant wheat and was chosen for further analysis. The gene shared very high sequence
similarity to an O. sativa HSP70 gene and was called TaHlp01 (Triticum aestivum Heat shock
Like Protein 01). TaHlp01 was inducibly expressed upon infection of resistant wheat with
leaf rust as well as yellow rust but its expression remained constant in the infected
susceptible cultivars. This indicated that the regulation of expression is dependent on the
presence of the resistance locus within the resistant cultivars. A transient repression of
TaHlp01 expression was found during the later stages of infection in both the IR and IS
plants that were similar to a transient repression of TaHlp01 expression after Thatcher+Lr34
plants were treated with salicylic acid. TaHlp01 expression was also found to be induced by
heat stress, indicating a possible role during heat stress.
A possible interplant communication event was also examined. It was found that infected
plants were able to induce the defence response of uninfected plants. This communication between infected and uninfected plants was more effective between plants of the same
cultivars than between different cultivars. It appears as if resistant plants were able to
induce a more controlled defence response than susceptible plants. When uninfected
resistant and susceptible plants exposed to infected plants, was infected themselves, they
exhibited a more resistant phenotype compared to plants that was not exposed. The
communication event during this interaction most likely involves jasmonic acid.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-12112007-141020 |
| Date | 11 December 2007 |
| Creators | Appelgryn, Johannes Jacobus |
| Contributors | Prof ZA Pretorius, Dr B Visser |
| Publisher | University of the Free State |
| Source Sets | South African National ETD Portal |
| Language | en-uk |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.uovs.ac.za//theses/available/etd-12112007-141020/restricted/ |
| 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 Free State 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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