To meet the nutritional requirements of a growing population, world agricultural output must increase by 70-100% by 2050. However, worldwide wheat yields are close to reaching a 'glass ceiling'. In order to meet the challenges of a rapidly growing population, scarcity of resources and a trend toward high-protein diets, traditional agriculture has looked towards molecular biology for insight and innovation for the future. Studying the mechanisms underlying DNA damage and repair is crucially important to facilitating generation of novel variation and developing breeding techniques. The Mismatch Repair (MMR) system is a highly-conserved series of pathways responsible for maintaining genomic integrity in prokaryotes and eukaryotes. The constituent proteins repair DNA mismatches and prevent meiotic recombination between homoeologous sequences. Work in Arabidopsis, tobacco and tomato has shown that plants with an impaired MMR system accumulate point mutations and undergo increased homoeologous recombination, which may be useful in breeding programs. Two key MMR genes are explored: MutS Homologue 2 (MSH2) acts as a heterodimer with MSH3, MSH6 or MSH7 to detect point mutations, insertions and deletions. Post Meiotic Segregation increased 2 (PMS2) is a homologue of the MutL gene, which co-ordinates repair of mismatches. The two genes were cloned and sequenced from elite cultivar Cadenza, and the sequences subsequently compared to next generation sequencing data from Chinese Spring. Three homoeologous copies of each gene were identified in the genome of wheat, and two of these were sequenced from the transcriptome. The expression of MSH2 was studied using qPCR in the transcriptome of Cadenza and four gamma-irradiated deletion lines, generated in a Paragon background. The four deletion lines showed varying responses: from down-regulation of MSH2 expression by 57% to upregulation by 82%. The expression of the individual homoeologues of MSH2 were also explored using a qPCR based method and by examining RNAseq data, but this was inconclusive.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:681489 |
| Date | January 2014 |
| Creators | Lewis, Rebecca Sian |
| Publisher | University of Bristol |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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