Directed evolution of a plant immune receptor for broad spectrum recognition of pathogen effectors

Rapid development of immune receptors that protect crops from emerging pathogens is a paramount goal. We applied high throughput directed evolution to the ligand binding domain of the rice immune receptor Pik1 to engineer affinity for a wide range of effectors from the fast-evolving fungal pathogen Magnaporthe oryzae . Engineered domains showed affinity for variants of the M. oryzae effector Avr-Pik that previously evaded detection by known rice alleles of Pik1. Additional rounds of mutagenesis and selection yielded a Pik1 domain that binds all tested Avr-Pik variants as well as the evolutionarily divergent effector AvrPiz-t. Our results demonstrate the potential of directed evolution to accelerate development of broad-spectrum pathogen resistance in crops and contribute to global food security.