Candidate Effector Proteome of the apoplastic space of wheat leaves infected with leaf rust (Puccinia triticina)

The fungus Puccinia triticina (Pt) is an obligate parasite that causes leaf rust on wheat. This disease occurs annually and potentially results in large yield losses, although it can be managed through fungicides and genetic resistance in the host. Rust populations consist of genetically determined races and when new races evolve they can sometimes overcome the host’s defences and cause epidemics – a problem exacerbated by monoculture farming. Pt enters wheat leaves through stomata and colonizes the apoplastic space with hyphae, which in the early stages of infection communicate with the host and attempt to evade the host immune system. The main components of this interaction are small, cysteine-rich effector proteins. The host in turn produces its own set of defence proteins that try to prevent pathogen invasion. Pathogen effector proteins and their cognate host resistance proteins are thus engaged in a kind of biological arms race where the effector proteins constantly evolve to evade the host resistance proteins, which in turn also evolve to target newly developed effector proteins. We are analysing both label-free and iTRAQ-labelled plant-pathogen proteomes, taken from both compatible (i.e. virulent) and incompatible (i.e. avirulent) Pt races on the same line of wheat, at various time-points post-infection. Although this approach is delivering candidate proteins, they still have to be verified either as pathogen effector proteins or as host defence proteins. This presentation focuses on LC-MS-based identification of these candidate proteins.