The ability to induce defenses in response to pathogen attack is a critical feature of immunity in any organism. Nucleotide-binding leucine-rich repeat receptors (NLRs) are key players in this process and have evolved to perceive the occurrence of non-self activities or foreign molecules. In plants, coevolution with a variety of pests and pathogens has resulted in repertoires of several hundred diverse NLRs in single individuals and many more in populations as a whole. The mechanism by which defense signaling is triggered by these NLRs is poorly understood. Here, Wróblewski et al. show that upon pathogen perception, NLRs use their N-terminal domains to transactivate other receptors. Plant NLRs oligomerize upon activation, similar to the vertebrate NLRs; however, consistent with their large number in plants, their complexes are highly heteromeric. Also, in contrast to metazoan NLRs, their N-termini, rather than their centrally located nucleotide-binding (NB) domains, mediate initial partner selection. The authors propose that a highly redundant network of NLR interactions provides resilience to perturbation by pathogens. The image shows an Arabidopsis thaliana plant infected with Tobacco Rattle Virus (TRV) harboring a sequence encoding Green Fluorescent Protein. The glowing patterns on the leaves mark tissue infected with the virus. The study used TRV both as a model pathogen and as a vector to deliver NLR fragments to plant cells.

Image Credit: Tadeusz Wróblewski