Characterising Mismatch Repair in Wheat Varieties

Worldwide wheat yields are close to reaching a ‘glass ceiling’. In order to meet the challenges of a rapidly growing population, increasing scarcity of resources and a general trend toward high-protein diets, traditional agriculture has looked towards the field of molecular biology for insight and innovation for the future. Studying the mechanisms underlying DNA damage and repair is crucially important to understanding their roles in biology; facilitating generation of novel variation and inspiring new breeding techniques. The Mismatch Repair (MMR) system is vital to genomic integrity, repairing DNA mismatches and preventing meiotic recombination between homoeologous sequences. Work in Arabidopsis and tomato has shown that plants with an impaired MMR system undergo three times as much recombination between homeologous sequences varying by up to 10% as wild type varieties.

There are five parallel MMR mismatch-detecting pathways in plants, each targeting different kinds of mismatch. The study target, MSH2, is a component in all five. The cDNA was cloned and sequenced from cultivar Cadenza. These data and genomic sequencing data were used to confirm that the gene has three homoeologous copies in the hexaploid variety, in addition to a partial pseudogene. The expression levels of the homoeologous copies of the gene have been characterised by qPCR in the hexaploid, in addition to four deletion lines. The deletion lines show a variety of expression responses, suggesting their potential usefulness for breeding programs. Future work will examine RNAi lines for elevated mutation levels using Next Generation sequencing; and development of a mismatch repair assay.