Plant pathogen effector proteins and their host targets: Functional studies and manipulation to generate enhanced resistance

As global population expands, so does its demand for food. This will require vast amounts of plant-derived calories. This increased pressure means it is vital that we do more with less; less land, less water, less chemical input and less labour. One major threat to crop production is posed by plant pests and pathogens. In particular, filamentous plant pathogens – oomycetes and fungi – are among the most devastating organisms known to agriculture. With their rapidly evolving genomes which specialise in breaking plant immune systems and chemical control methods, control of these pathogens is becoming extremely problematic. Especially as they often encounter crops in monoculture. An often overlooked potential strategy for developing pathogen resistance is manipulation of the host targets of plant pathogen effector proteins. In order to manipulate such targets to condition enhanced resistance, one must first develop a sound understanding of the interaction between effector and target, the target’s function in planta and which processes are being perturbed by the interaction. A previously discovered interaction between a P. infestans RXLR effector and a host MAPK known to be a positive regulator of immunity, where the effector acts to perturb positive regulation of immunity, is used here to investigate the possibility of manipulating a host target for enhanced immunity. Effector-insensitive variants were produced and characterised, prior to expression in CRISPR-edited tomato plants. We tentatively suggest that at least one variant may condition enhanced resistance. Another interactor of the same effector protein was investigated for its role in immunity and evidence suggesting it may function as a helper of the effector is presented. Additionally, the expression, purification and crystallisation of native and heavy atom derivatives of a candidate effector protein from B. graminis f.sp. hordeii is demonstrated