Title page for ETD etd-05092005-164928

Document Type Doctoral Thesis
Author Lacock, Lynelle
URN etd-05092005-164928
Document Title Profiling of gene expression in bread wheat (Triticum aestivum L.) line PI 137739 in response to Russian wheat aphid (Diuraphis noxia Mordvilco) feeding
Degree PhD(Genetics)
Department Genetics
Advisor Name Title
Prof A-M Botha-Oberholster Committee Chair
  • DNA microarrays
  • plant gene expression
  • wheat disease and pest resistance
  • Russian wheat aphid
  • wheat genetic engineering
  • genetic regulation
Date 2007-07-24
Availability unrestricted
This thesis investigates the effect of Russian wheat aphid (RWA; Diuraphis noxia) infestation on the defence responses of the bread wheat line, PI 137739, on a molecular level. PI 137739 is known to contain the RWA resistance gene, Dn1. The study was conducted by utilising and combining a vast array of molecular biological techniques.

Chapter 1 introduces the reader to a summary of the resistance responses observed within infested plants. A detailed description of the Russian wheat aphid follows and the genes responsible for RWA resistance in wheat is discussed. A brief report of research performed on the bread wheat genome is given and the biochemical defence responses of plants against insect infestation are discussed. This is followed by a concise description of resistance (R) genes and resistance gene categories in plants. The last discussion concerns microarray technology, a molecular tool utilised during this study.

Chapter 2 aims at identifying genes involved in resistance against RWA infestation; specifically, genes containing the conserved nucleotide binding siteČleucine rich repeat (NBS-LRR) motif. Genomic, as well as complementary DNA (cDNA), was utilised in order to compare functional gene expression in wheat infested with the RWA. This was executed by employing PCR-based methods, single-pass sequencing and basic local alignment search tool (BLAST) analyses.

Chapter 3 introduces suppression subtractive hybridisation (SSH) as a tool to further identify NBS-LRR or other resistance-related sequences in RWA infested wheat plants. SSH allows the comparative analysis of differential gene expression in RWA infested and uninfested wheat in order to identify resistance-Črelated genes expressed in the infested, resistant wheat plants.

The effect of RWA infestation on wheat resistance responses was examined further in chapter 4 through microarray analysis. The aim was the introduction and establishment of the microarray technique and to test the feasibility of using microarrays for differential gene expression and regulation studies. Microarray slides were assembled in order to monitor the up- and downČregulation of genes at different time intervals - day 2, day 5 and day 8 - of RWA infestation. Clones isolated throughout this study were assembled on microarray slides and probed with control and RWA infested RNA. Differential gene regulation was assessed and further confirmed through Northern blot analyses, as well as quantitative real-time PCR.

The thesis concludes with a general summary of the results obtained in chapter 5 and future prospects are outlined.

ę 2003 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria.

Please cite as follows:

Lacock, L 2003, Profiling of gene expression in bread wheat (Triticum aestivum L.) line PI 137739 in response to Russian wheat aphid (Diuraphis noxia Mordvilko) feeding, PhD thesis, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-05092005-164928/ >


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