Engineering an auto-activated R protein that is in vivo activated by a viral protease

Autonomous hypersensitive responses (self-HRs) are caused by constitutively active R proteins. In this study, we identified an auto-activated form of the R gene Pvr9 (autoPvr9); the auto-activation results from an amino acid substitution between its NBS and LRR domains. Self-HR was strongly reduced or completely inhibited by fusion of an extra peptide to the autoPvr9 N-terminal or C-terminal, respectively. When an NIa recognition site was placed between autoPvr9 and the extra peptide, the fusion construct could trigger an NIa-dependent HR. Several C-terminal fusions were tested, but only those that maintained detectable protein expression were capable of an NIa-dependent HR. Our results suggest the potential for transforming malfunctioning and auto-activated R proteins into a new construct targeting potyviral NIa proteases.