Mismatch repair (MMR) is responsible for the repair of basepair mismatches which have arisen during replication. MMR thus reduces the frequency of mutations in the genome. MMR also recognizes mismatches which are formed in heteroduplex DNA during recombination. Because of this MMR creates a barrier for homeologous recombination between related genomes. A key protein in MMR is MSH2.
In this project, the effect of MSH2 deficiency on the appearance of spontaneous mutations in the genome will be examined in potato. To do this the MSH2 gene will be silenced by artificial miRNAs (amiRNAs) and afterwards the presence of a mutator phenotype will be examined. This can be observed in further generations by the occurrence of phenotypic instability (e.g. albino mutants) and genomic instability (e.g. simple sequence repeat (SSR) instability). It will also be possible to screen for mutants with economically important characteristics, such as salt or drought tolerance, improved nutritional value, etc.
Second, the effect of MSH2 deficiency on the frequency of homeologous recombination during protoplast fusions between S. tuberosum and S. chacoense will be examined. To achieve this objective protoplast fusions will be carried out with both wildtype and MSH2 deficient parents. The frequency of recombination will subsequently be assessed by analyzing the segregation of specific molecular markers (SSRs).