Signaling Events During the Establishment of Symbiosis Between Arbuscular Mycorrhizal Fungi and Plant Roots

The most prevalent microorganism association in terrestrial plants is the symbiosis between arbuscular mycorrhizal fungi (AMF) and plant roots. This implies that the genetic background for establishing this symbiosis was developed in the early phases of land plant evolution. A symbiosis faces several challenges, such as penetrating plant cells and overcoming their defense mechanisms. At the same time, it must activate some developmental pathways for symbiotic structures along with membrane transporters required to exchange nutrients and metabolites between two partners. This chapter discusses the response of plants to fungal signals, the function of receptor molecules, and other actors that play a crucial role in the signaling pathways. Ultimately, these pathways result in the expression of symbiosis-specific genes and the formation of symbiosis-specific structures.