Signals and cues in the evolution of plant–microbe communication

[Display omitted] •Communication depends on signals and cues, terms that are often confused.•Organisms can increase their fitness by hijacking and manipulating communication.•Parasitic and myco-heterotrophic plants use plant–microbe signals as cues.•Plants receive cues from other plants via common arbuscular mycorrhizal networks. Communication has played a key role in organismal evolution. If sender and receiver have a shared interest in propagating reliable information, such as when they are kin relatives, then effective communication can bring large fitness benefits. However, interspecific communication (among different species) is more prone to dishonesty. Over the last decade, plants and their microbial root symbionts have become a model system for studying interspecific molecular crosstalk. However, less is known about the evolutionary stability of plant–microbe communication. What prevents partners from hijacking or manipulating information to their own benefit? Here, we focus on communication between arbuscular mycorrhizal fungi and their host plants. We ask how partners use directed signals to convey specific information, and highlight research on the problem of dishonest signaling.