Mutations that abolish Pikm-1:ancHMA autoactivity are inadequate for testing the impact of AVR-PikD binding on Pikm-mediated immunity

This Technical Note complements our paper on the evolution of the integrated HMA domain of the Pik-1 immune receptor (Białas et al., 2021). Pikm-1:ancHMA is autoactive when co-expressed with Pikm-2 and therefore cannot be directly used to study how changes in binding to the AVR- PikD effector affect the activation of immune responses. Here, we identified mutations that abolish Pikm-1:ancHMA autoactivity. Unfortunately, these mutations either (i) perturbed the response to AVR-PikD or (ii) affected protein stability. This precluded reliable studies of how the strength of AVR-PikD binding to Pikm:ancHMA correlates with activation of cell death response.