Characterisation of a secretory P-type ATPase required for fungal pathogenesis and induction of host defence

The world's most serious diseases of plants are caused by fungi. These diseases affect many of the crops we depend on for food, such as wheat, rice, barley, potatoes, and important fruits and vegetables. To control crop diseases, farmers currently plant new crop varieties which have been selectively bred to be disease-resistant, or spray their crops with modern systemic fungicides. Neither of these control measures are completely effective, however. Disease-resistant crop varieties are normally overcome by disease within 2-3 growing seasons, and fungicides are expensive, can be environmentally damaging, and fungi tend to develop resistance to new chemicals very quickly. Because of these problems, we need to think of new ways to control plant diseases. These new disease-control measures will have to be environmentally safe, economically viable and above all, highly effective. To develop new disease-control strategies for curing plant diseases, we first need to understand the biology of the fungal agents that cause plant diseases. This project is concerned with understanding the biology of rice blast disease, which destroys enough rice every year to feed 60 million people. The aim of research n my laboratory is to understand this disease and the fungus that causes it and to develop control strategies to fight the disease. The thread-like cells formed by the fungus that causes rice blast are very effective at colonising plant tissues and can do so without the plant immune system being immediately activated. When fungal pathogens invade living plant tissue, we believe that they secrete proteins that help them to evade the plant's defences, alter plant cell signalling, and subvert plant metabolism. Identifying these fungal proteins, and understanding the process of fungal secretion during rice blast disease, are important aims of this project. If we can understand the fungal secretory process and how it functions during plant infection and induction of the plant's defence reactions, then this will provide a means of potentially controlling the spread of the disease

The aim of this project is to determine the role of the MgApt2 P-type ATPase in delivery of fungal effector proteins by the rice blast fungus Magnaporthe grisea. The project builds on the observation that mgapt2 deletion mutants are unable to cause rice blast disease and also cannot induce a hypersensitive reaction during an incompatible interaction. This project will investigate whether MgApt2 is required for delivery of the Avr-Pi-ta avirulence gene product during interaction with rice cultivars carrying the Pi-ta resistance gene. The transport of Avr-Pi-ta will also be investigated in detail using a GFP-fusion protein and by conditionally silencing MgApt2 during plant infection by M. grisea. The role of MgApt2 in Golgi function and exocytosis in M. grisea will be explored based on localisation studies with MgCdc50 and clathrin, and by yeast complementation studies. The most abundant cargo protein transported by the MgApt2-dependent exocytotic pathway will be identified using sub-cellular fractionation of M. grisea infection structures, protein separation and mass spectrometry. The corresponding genes will be investigated by targeted gene replacement, and gene expression studies. Collectively, the project will provide a new understanding of the mechanisms by which fungal proteins are delivered into host plant cells during plant infection.