Dating in the dark: how roots respond to fungal signals to establish arbuscular mycorrhizal symbiosis

The arbuscular mycorrhizal symbiosis that involves most plants and Glomeromycota fungi is the result of a complex exchange of molecular information, which commences before the partners are in physical contact. On the one hand, plants release soluble factors, including strigolactones that activate both the metabolism and branching of the fungal partners. On the other hand, fungi use compounds that trigger the signaling transduction pathways that are required for the symbiotic modus of plant cells. Here we describe some of the recent discoveries regarding the fungal molecules involved in rhizospheric conversation, and the way in which they are perceived by their hosts. We conclude that similar signaling molecules may have different meanings, depending on the context. However, at the end, specificity must be maintained to ensure appropriate partners enter symbiosis.

► Plant roots and arbuscular mycorrhizal fungi (AMFs) exchange signals which are reciprocally perceived.
► Nod-like lipochitooligosaccharides have been identified as important fungal bioactive molecules.
► Plants perceive microbial factors thanks to a pathway, which is shared in AMs and N-fixing symbiosis.
► Changes in calcium concentration lead to spiking patterns with diverse features.