April 11, 2019 // Guarded and Targeted: Investigating the role of MACPF domain proteins in plant immunity

Irina Sementchoukova, MSc candidate, Monaghan Lab, Dept Biology, Queen's 

Pseudomonas syringae is a bacterial pathogen that causes disease in a broad range of plant species.  As a part of its infection strategy, P. syringae releases virulence factors called effectors into plant cells to disarm host defenses. In response to effector sabotage, plants evolved intracellular NUCLEOTIDE BINDING AND LEUCINE RICH REPEAT RECEPTORS (NLRs) that ‘guard’ the integrity of critical immune signalling components prone to be effector targets. When no damage is detected, NLRs remain in the ‘OFF’ state, and only turn ‘ON’ when perturbations are detected in the guarded protein. Activated NLRs typically result in a form of programmed cell death at the site of infection that protects surrounding uninfected tissues. MEMBRANE ATTACK COMPLEX/PERFORIN (MACPF) proteins are well known agents of defense in the mammalian immune system, though the molecular function of this protein family in plants has not been established. The model plant Arabidopsis thaliana encodes four MACPF domain proteins, and genetic evidence suggests that at least two of these proteins are involved in the plant immune response. Interestingly, loss-of-function mutations in these loci result in hyperactive immune signaling and cell death, reminiscent of dysregulated NLR activation.  My project has thus been focused on determining if MACPF proteins may be effector targets guarded by plant NLRs.