Coordination of PTI and ETI in legume–rhizobium mutualism

The plant immune system plays crucial roles in interactions with microbes— both pathogenic and beneficial. During the past few decades, great progress has been made in understanding the molecular mechanisms of plant immune responses, including during legume–rhizobium mutualism. Here, we summarize recent progress uncovering the roles of the two layers of plant immunity, pathogen-triggered immunity (PTI) and effector-triggered immunity (ETI), in the association between legumes and rhizobia. We propose that crosstalk occurs between PTI and ETI in legumes to regulate symbiotic interactions with rhizobia. This concept enhances our understanding of the molecular mechanisms underlying the relationships between plant immunity and legume–rhizobium mutualism.