Grant: Discovery Grants Program - Individual

Our long-term goal is to understand how fungal pathogens cause diseases on crops and trees of economic importance to Canada. Ultimately, we want to contribute to new strategies for plant protection and sustainable agriculture. We study pathogens that attack cereal crops of relevance to Canada including the corn pathogen Ustilago maydis . This fungus causes a dramatic disease in which ears of corn are converted to large tumors that eventually fill with black masses of fungal spores (called smuts because their black, sooty appearance). These spores spread the disease and contaminate grain from uninfected plants. U. maydis is a threat to corn production and it is also a valuable experimental organism for understanding other how related fungal pathogens cause substantial losses in crop yield and quality for wheat, barley and oats. In our program, we specifically investigate the formation and proliferation of specialized cells (filaments) of U. maydis that are required to invade plants. We also want to understand how the pathogen senses the environment of the plant host and how it obtains nutrients after invasion. Our work led to the discovery of endogenous fungal factors (mating signals), lipids and phosphate as signals and nutrients that influence filamentous growth during infection. Recently, we employed state of the art molecular technology to identify changes in expression during disease for all of the approximately 6,500 genes of U. maydis and all of the approximately 32,000 corn genes. This work revealed key features of nutrient acquisition by the fungus and important defense changes in the plant. Importantly, we discovered that infection by the pathogen results in destruction of the key plant structures (chloroplasts) required for metabolism (photosynthesis for example) and defense. To take advantage of our discoveries, we plan to use the latest technologies for measuring proteins to determine which of the predicted pathogen proteins (out of 6,500) actually enter chloroplasts to cause damage and block plant defense. We performed a preliminary experiment to confirm that we can identify these proteins and we now have a preliminary list of candidates. In parallel, we plan to measure changes in chemicals associated with chloroplast function and defense using analytical methods. Together, these experiments will provide a detailed picture of how U. maydis attacks corn plants. Subsequently, we will use genetic techniques to block the ability of specific U. maydis proteins to damage chloroplasts, and we will use biochemical techniques to determine the mechanism(s) of action of key proteins. It is important to identify these proteins because their characterization may reveal new strategies to control fungal diseases and protect crops.