Calcium signaling plays a fundamental role in plant immune responses.Various calcium sensors have been characterized to relay and/or decode pathogen-induced calcium signals.Autoimmune mutants are useful resources for the dissection of plant immune systems,which have allowed researchers to access in-depth mechanisms of defense signaling.Recent discoveries in this rapidly evolved field have revealed new elements that could help understand the signaling mechanisms mediated by the nucleotide-binding oligomerization domain-like receptors (NLRs).Here,we briefly overview calcium signaling mutants that exhibit autoimmune phenotypes and focus on discussing AtSR1/CAMTA3-regulated immune signaling,especially how this calcium sensor acts as a guardee monitored by NLR proteins.