Molecular mimicry of a pathogen virulence target by a plant immune receptor

Plants and animals respond to pathogen attack by mounting innate immune responses that require intracellular nucleotide-binding leucine-rich repeat (NLR) proteins. These immune receptors detect pathogen infection by sensing virulence effector proteins. However, how receptors evolve new recognition specificities remains poorly understood. We found that the plant NLR MLA3 (Mildew locus a 3) has evolved to recognize a pathogen effector by acting as a molecular mimic of an effector virulence target, thereby triggering an immune response. By introducing the mimic's binding interface into the wheat stem rust resistance protein SR50, we bioengineered a chimeric receptor with dual recognition activities that conferred resistance to two major cereal pathogens in barley transgenic lines. These results demonstrate that molecular mimicry by immune receptors can be harnessed to engineer multiple disease resistance.