‘Decoy’ engineering is an emerging strategy that introduces novel, new-to-nature disease resistance traits against crop plant pathogens. In this approach, a protease recognition sequence within a host protein, PBS1, is replaced with a protease cleavage sequence recognized by other pathogen-secreted proteases, thereby generating a PBS1 decoy variant. Proteolytic cleavage of the PBS1 decoy protein by the pathogen-secreted protease activates a disease resistance protein, thereby conferring resistance to the pathogen. This strategy has been successfully deployed in Arabidopsis and soybean to confer resistance against both bacterial and viral pathogens. Similar to Arabidopsis and soybean, wheat and barley contain multiple PBS1-like proteins that, when cleaved, activate the disease resistance protein PBR1. Therefore, we predict the decoy engineering strategy can be extended to these crop plants with the goal of introducing novel disease resistance traits to Fusarium graminearum based on the recognition of F. graminearum effector proteases. To the end, we have identified an effector protease from F. graminearum, which we have termed FgTPP1, that is expressed during early symptomless stages of disease development. Subcellular localization analyses showed that this effector protease localizes to the chloroplast stroma, suggesting that this protease is translocated into wheat cells during infection. Importantly, knockout of FgTPP1 significantly reduced F. graminearum virulence in wheat spikes, indicating FgTPP1 plays an important role in fungal virulence. Future work will involve identifying preferred cleavage site specificities of FgTPP1 and testing whether cleavage of the wheat and barley decoy variants by FgTPP1 activate PBR1-dependent immune responses.

Acknowledgements

This research was funded by the United States Department of Agriculture, Agricultural Research Service (USDA-ARS) research project 5020-21220-014-00D, the U.S. Wheat and Barley Scab Initiative grant to SRS and MH (award number FY20-SC-022), and an appointment to the Agricultural Research Service Research Participation Program administered by the Oak Ridge Institute for Science and Education (ORISE). The funding bodies had no role in designing the experiments, collecting the data, or writing the manuscript. USDA is an equal opportunity provider and employer.