Wheat zinc finger protein TaZF interacts with both the powdery mildew AvrPm2 protein and the corresponding wheat Pm2a immune receptor

Plant defense responses to pathogens are induced after direct or indirect perception of effector proteins or their activity on host proteins. In fungal-plant interactions, relatively little is known if in addition to avirulence effectors and immune receptors, other proteins contribute to specific recognition. The nucleotide-binding leucine-rich repeat (NLR) immune receptor Pm2a in wheat recognizes the fungal powdery mildew effector AvrPm2. We found that the predicted wheat zinc finger TaZF interacts with both the fungal avirulence protein AvrPm2 as well as the wheat NLR Pm2a. We further demonstrated that the virulent AvrPm2-H2 variant does not interact with TaZF. TaZF silencing in wheat resulted in a reduction but not loss of Pm2a-mediated powdery mildew resistance. Interaction studies showed that the LRR domain of Pm2a is the mediator of the interaction with TaZF. TaZF recruits both Pm2a and AvrPm2 from the cytosol to the nucleus, resulting in a nuclear localization of Pm2a, TaZF and AvrPm2 in wheat. We propose that TaZF acts as facilitator in the Pm2a-dependant AvrPm2 effector recognition. Our findings highlight the importance of identifying effector host targets for the characterization of NLR-mediated effector recognition.