NLRs constitute intracellular immune receptors in both plants and animals.Direct or indirect ligand recognition results in formation of oligomeric NLR complexes to mediate immune signaling.Over the past 20 years,rapid progress has been made in our understanding of NLR signaling.Structural and biochemical studies provide insight into molecular basis of autoinhibition,ligand recognition,and resistosome/inflammasome formation of several NLRs.In this review,we summarize these studies focusing on the structural aspect of NLRs.We also discuss the analogies and differences between plant and animal NLRs in their mechanisms of action and how the available knowledge may shed light on the signaling mechanisms of other NLRs.