Throughout their life cycle, plants have to respond appropriately to diverse microorganisms. While living alongside harmless commensals and warding off disease-causing and nutrient-seeking pathogens, plants also engage in intimate endosymbiosis with microorganisms that deliver scarce mineral nutrients. In particular, the mutually beneficial symbiosis with arbuscular mycorrhizal fungi (AMF) is prevalent and is thought to have been instrumental for plant colonization of the terrestrial landscape ca. 450 million years ago. Until today, it remains important for plant nutrition (1). The molecular mechanisms that underlie the decisions made by plants to engage with the appropriate microorganisms are an area of intense research, and knowledge gleaned could enable the development of crops that benefit more from and are compromised less by their microbiomes.