NAD+ Cleavage: TIR Domain-Containing Resistance Proteins in Action

Plant resistance proteins play a key role in detecting pathogen infection and activating plant defense. Two recent papers by Horsefield et al. and Wan et al. revealed that the TIR domain in resistance (R) proteins functions as an NAD+-cleaving enzyme. This enzymatic activity is induced by pathogen recognition and is indispensable for the R protein-dependent cell death response.