Sean Chapman

The major focus of my research is on developing durable resistance against the potato pathogen Phytophthora infestans that causes late blight, the most important disease of potatoes. Work at the James Hutton Institute has identified proteins secreted by the pathogen to overcome innate host resistance and some of these effector proteins have been shown to be essential for pathogenicity. In response plants have evolved resistance proteins that recognise effector proteins and trigger resistance responses to prevent infection. In turn pathogens have evolved effector alleles that evade R gene recognition.

To combat the evolution of P. infestans populations that overcome resistances deployed in currently grown cultivars new sources of resistance from wild potato species are bred in. A possible new approach is to genetically engineer R genes to recognise virulent effector alleles. As a proof of principle the potato R3a resistance gene, which recognises the evolutionarily conserved and non-redundant effector protein Avr3a has been subjected to DNA Shuffling. This process, which has been used previously in a number of projects at the James Hutton Institute including the development of the novel compact, fluorescent reporter protein iLOV, mimics the natural evolutionary processes of mutation, recombination and selection, but on accelerated timescale. Shuffling of R3a has produced mutants that, unlike the natural gene, can recognise both virulent and avirulent effector alleles. The protection provided to potatoes by these new genes is currently being assessed and the approach is being extended to other resistance genes.

In addition to my personal research I manage the Institute’s transmission electron microscope facility. Thus, I have been involved in a diverse array of projects including mapping of pectic epitopes in cell walls of potato tubers with regard to texture; localisation of human enteric pathogens in plant roots to investigate colonisation; immuno-localisation of an effector protein; analysis of ultra-structural changes resulting from potato mop-top virus infection; characterisation of plant derived virus-like particles for vaccine use and nanoparticles produced in plants or using plant extracts.